"Powergamer" also known as "Spike" by Magic players, a name chosen specifically because it sounds all Serious Business and boring, is a term describing players who are interested in winning and, more to the point, winning big. Exactly how they do this depends on the game.
Powergamers who play RPGs generally attempt to make their characters as effective as possible within the game's framework, possibly (but not necessarily) by exploiting broken or badly worded rules. The term is usually used pejoratively, suggesting that the player in question only cares about the mechanical power of their character and this comes at the expense of roleplaying. Although there is nothing intrinsic to powergaming that inhibits good roleplaying (aka. the Stormwind Fallacy), such behavior is a magnet for That Guy because it allows him to steal the spotlight, lord it over to other players, annoy the GM and/or generally suck the fun out of the game for everyone else.
In wargaming: powergamers are less likely to be referred to as such due to its association with level-scaling systems, and are typically referred to as "tourneyfags", "WAAC players" (standing for Win At All Costs) or merely "competitive players" which are generally neutral terms. Powergamers are especially hated in the wargaming community as they typically exude a noxious odor, have no interest in fun besides their own and are the number one reason people new to the hobby ragequit immediately.
A somewhat milder term with a similar meaning is "optimiser", which generally lacks the negative connotations of powergamer, in that they won't typically suck the fun out of anything they touch. An optimiser wants to beat the game, but at least realizes you need to have at least two to play it so he isn't a jerk about it.
At the other end of the scale is the "twink" or "munchkin", which is almost always used to refer to someone who cares only about mechanical power (to the exclusion of roleplaying), or is willing to outright cheat if he thinks he won't get caught, or there will be no consequences if caught, as is demonstrated by the "Munchkin" series of card games by Steve Jackson Games.
Everyday powergamers are easily forgiveable, since there is a healthy respect for the way that any given game system functions, and their actions are perfectly excusable since the rules allow (and can be argued "encourage") them to do so. Depending on the setting or ruleset, a powergamer can garner a healthy measure of accolade for coming up with new levels of "optimal" play.
By contrast, Munchkins have a marked tendency to be more creative in their interpretations of rules; where a typical powergamer would look at a ruleset and use it to their maximum advantage, a munchkin's typical response to their detractors is that nothing in the rules say that they cannot do something.
In wargaming, the equivalent to munchkin would be WAAC (Win At All Cost) players, who focus almost entirely on overpowered/broken units or rules or armies, rather than attempting to create an efficient or optimal army list.
True Munchkins rarely, if ever, gain positive recognition for their accomplishments.
Identifying a Powergamer
Everyone who plays a game with a rule-based system (whether competitive or cooperative) is a powergamer to one degree or another. As everyone who plays wants to do their best and so long as people know the rules they can understand what is comparatively better than another, so unless someone gets a kick about playing the underdog or seeing others outperform themselves, it's simply in the nature of the system.
Habitual powergamers might argue that they are not powergaming at all and that they are just playing the same way as everyone else, but are easy to spot based on their behaviour and appearance, which is generally the same regardless of which system/ruleset they are using.
In systems which undergo regular revisions or receive frequent updates, powergamers will often stand out due to their fickle attitudes. Often becoming obsessed with the next "new" rulebook/codex/splatbook which will either be an improvement over anything previously released or is new enough that it has not been effectively countered or debunked by the community at large. In these situations, a gamer who requests a re-roll of his character or sells his old army on ebay to fund his next one are generally going to be powergamers.
- Note: it doesn't have to be freshly released rules or player options to count as "new", but can also be from the point at which the player discovers that he can do something new that he starts changing his attitudes in favour of his latest obsession.
Lack of imagination when it comes to character/army builds is also a clear indication; people who hunt internet forums/help-sites for optimal builds tend to be powergamers, as it shows that the player is more interested in "winning" than actually playing the game in their own fashion. (see the rage summary below) Powergamers who also rely too heavily on public-domain builds can also reveal themselves to be poor players and tend to have the most difficulty adjusting when someone else presents them with a unique situation or when new rulebooks get released (but then they jump ship)
They also tend to be quite vocal in their disappointment if they or others alongside them are not playing "optimally". For example: in RPG sessions if the group healer is not playing a build that they think is optimal for healing and could be bringing the group down. This is extremely visible in MMORPGs where non-optimal players tend to get kicked from raid groups. On the tabletop, they'll tend to complain that their losses during games are because they don't yet own the right combination of models/units (but will "soon") or that you cheated. (Either way, it's not their "fault" that they lost)
Considering the issue from a different angle, Powergamers usually like to brag about the killing efficiency of their characters, putting emphasis on the hard work necessary to support their uber character. Interestingly, as soon as it is touched upon the extreme efficiency-build, they usually get very defensive about it. Watch out for someone defending their character as "not imba" before the accusation is made.
Taking this further, players who get called out on their powergaming will often go to obsessive lengths to tell you how their character is NOT the result of powergaming or munchkin-fu and will have a defence seemingly prepared before the question gets raised. They'll often immediately go into great detail about what their character is bad at, or cannot do as well as other party members to try and convince you why their character is balanced. Unfortunately for them, this has all the hallmarks of being a powergamer anyway, because obviously they've considered the issue at great length before getting into the argument; it's like they think the fact that they have a Dump Stat deserves positive recognition and would be like pointing out their Wizard cannot fight in melee as well as a Warblade, when that wasn't really the issue in the first place. Of course this would also be similar behaviour to how someone being unjustly accused of being a powergamer might react, especially if they are naturally prone to considering all the angles. Being aware of your models' own strengths and weaknesses does not automatically make one a powergamer, and sometimes you might just get fucked over by a bad match-up. Generally, just remember you could be wrong unless that kind of thing happens over and over.
If you've played against one in any game, was it fun? Did you like having your balls ground to a pulp? Fuck no. Nothing is worse than that guy who spams Abaddon AND Kharn AND three fucking Land Raiders because of a technicality. They're all dedicated transports? FUCK THAT NOISE, GTFO MY STORE. Or the guy who manages to get
4 5 6 7 21 riptides in a single list because of GWs vague rules.
Ever played against an IG armoured list? No? Pray you never do, because that list displays a level of asshattery (and disposable income) on a godlike level. Seriously, fucking TANKS as TROOP CHOICES?! OH FUCK THE FUCK OFF! Necrons don't care though so... Allies much?
Did you know that it's theoretically possible for a player in the original World of Darkness to have the powers of a vampire, a werewolf, and a mage at the same fucking time? Why even bring a fucking party?!
For anyone playing a game simply to have fun and enjoy a good story, a powergamer is your number one enemy. Avoid at all costs. They'll fuck your shit up six ways to Sunday and five ways to Monday simply because they can. The only cure for powergamers is exile; avoid, ignore and generally make it plain they are not welcome to your game/store/house/existence.
Dealing with Powergamers
Being the GM of a party with a munchkin/powergamer can be quite tricky, since it can radically unbalance the group in many situations. For example, if he's somehow got himself infinite (figuratively speaking) armor-class then introducing a hard hitting counter to him could be absolutely devastating to the rest of the group if they aren't also powergamers.
Best thing to do would be to speak to them away from the gaming table and discuss winding it back a notch, or at the very least concentrate his powergaming efforts onto just one thing in particular and stop being a do-it-all mary sue. Unless your powergamer is a dick you may find that this works best and keeps tears to a minimum.
Failing that, you can always read their character sheet to see precisely what will work against them, though this may require a lot of work on your part to piece it all together. The unkillable party tank may be weak against compulsions or fear effects, or the god-like wizard becomes useless in a magical dead-zone or wild-magic area, which would force him and the party to come up with more creative solutions rather than "throw the powergamer at it"
If that doesn't work or if you cannot find an easier solution, then a stern reminder is in order. A powergamer is beholden to the rules of the game, even if he twists them to his own advantage to create something more powerful than the sum of its parts. A good GM is but a bad GM is not. Still, When dealing with a fun-sucking powergamer, it's not bad GMing, it's saving the fucking game. You are the Neo to the gamer's Agent Smith and you can invent things on a case-by-case basis to give the powergamer a spanking.
- Unkillable PC Barbarian? Meet the "actually" unkillable barbarian with axe of instant death, he kills you but the party's weak-ass rogue could one-shot him to death by stabbing him in the neck. That's not in the rules you say? I'm the GM and can rationalise whatever I like in the world I built. That's not fair you say? Did you really think I'd let you walk over my game every week? Is that you Oberoni?
Can be harsh, but if your GM style is not harsh in the the first place (i.e: anything other than Killer GM) then your players should have realised that powergaming was absolutely unnecessary in the first place and that there isn't really a "winner" in a game that only goes on as long as the GM can be bothered putting up with you guys.
Of course the other side of the coin is definetely worth remembering as well. There is only going to be a game as long as people find it fun. And being rail-roaded by a DM and his army of NPCs who are better at everything than the PCs because they use magical DM powers that let them ignore the rules, then you probably won't have players for long. This holds especially true when it's done because the DM couldn't be bothered enough to actually make encounters that would be challenging for the group as a whole without ignoring the rules (when all he had to do was use his brain and target the big dumb guy with the huge sword with a "mental" spell.)
So all in all it's very important to look at what's going on and TALK to people about any problems that's perceived. If both parties are willing to actually listen in an attempt to understand and NOT just waiting their turn to respond, then you can almost always find a solution (unless one or both are petty cunts).
Just don't play with them and make certain that other people are aware of the sort of opponent they are too, so your friends can make the same decision. If you get no enjoyment out of the game there is no point in playing, wargaming is not a job or sport that requires your absolute commitment. Your opponent will find that they have no-one to play with either. Whoop-di-do if they've got an unbeatable spam list if no-one will give them the smug satisfaction of beating people stupid enough to play against them. This goes double for true munchkin players who exploit bad RAW to get advantages they shouldn't have.
Failing that, if there is no-one else to play with in your area, or if you are at a tournament that kind of requires your participation, if you can't beat them... join them. Unfortunately this means stooping to your opponent's level. If you need help with becoming your own worst nightmare, there are plenty of tactica and netlists out there which can help you to build your army. Just don't let it go to your head. Alternatively; just leave. Eventually there will be so few showing up to tourneys that either the offending players will stop coming (and therefore allowing tournaments to re-engage) or they'll be stuck in a room of their fellow cheeselords (named for the odor as much for the strategy) which is a private hell on its own.
In Card Games
Do what you would do with wargamers, don't play with that person who is playing that top dier netdeck who solely wants to beat you, just leave him alone and refuse to play, maybe go off and play Commander.
Examples of Powergamers/Munchkins
- Comic Book Guy from the Simpsons, when he makes custom Pokemon, Digimon, and/or Yu-gi-oh trading cards
- Sheldon Cooper from Big Bang Theory, who also uses custom cards, and munchkins his way around a group ban on "home-made" cards by making them at work.