Bag of Holding
A Bag of Holding is, as the name implies, a bag that holds things. However, due to its magical nature, it holds far more volume on the inside than it appears on the outside and will weigh only a fraction of its contents' mass. With it dungeon delvers and murderhoboes can stop worrying about encumbrance rules (gold coins in D&D used to be 1/10th of a pound) and deny they have a hoarding problem just a little longer.
It's explicitly named "Bag of Holding" for Dungeons & Dragons, but you'll find something similar in any RPG that has magic, or comparable system. It's just too damn useful not to have. It may have been made worse by early adventure video games, where you had to collect everything because you didn't know what might be a piece of a puzzle later.
Since it is such a common item for adventurers, and breaks physics in a very simple way, it is a lovely tool for gamebreaking.
The Necrons love this kinda stuff, what with their pocketdimensions and doors to infinity (and beyond). They even have a Pokéball for their lords and overlords, if they happen to encounter some dude they just really want to have in the collection.
There exists various other iterations of a bag of holding; one of the more common is the bag of tricks, which is much more akin to a "magic hat", in that it can be used to summon varying types of animals. Another one is the Mirror of Life Trapping which can automatically nabble you, yourself, for that pocket dimension; ejecting whatever else is in there, probably something equally powerful and (now) grouchy. Feel free to ask your mom about the portable hole.
Under no circumstances should you try to put a bag of holding into a portable hole, another bag of holding, or a Sphere of Annihilation. If you do, horrible things will happen that tend to annihilate everything within several miles.
This trope got expanded hard in X12: Skarda's Mirror, where the eponymous artifact-tier Mirror holds an entire army. Knights of the Dinner Table came to feature a similar item, wherein the ex-retainer Barringer has set up shop and now extorts the Knights if they want to store anything more in there.
Shitcannon of Holding
Let's say you have a bag of holding, 1,500 pounds weight limit. In feudal lands you can easily acquire 1,500 pounds of cattle manure to fill the bag completely.
Falling objects in D&D do 1d6 damage per 200lbs per 10 feet they fall. A falling object will accelerate to ~15 meters per second after 40 feet of falling. Remember this for later.
A human's normal movement rate in Dungeons & Dragons is 30 feet per round (6 seconds). If the human took the 'Running' feat, they can sprint to 5x their normal movement speed, or 150 feet in one round. With a Haste spell in effect, that is doubled to 300 feet in one round. 300ft / 6seconds =~ 15.24 metres per second.
So. One guy holds open the bag of holding in outstretched arms, pointing the mouth at some evil wizard. Other guy gets Hasted, runs at full tilt at the back of the bag. This will easily invert the bag, violently ejecting its contents at the imparted speed. The target the bag was aimed at will get 1,500 pounds of shit at a nice 15 meters per second, for (7.5 rounded up) 8d6 damage, x4 for the extra speed. That's a total of 32d6 of filth applied directly to the forehead, more than the evil wizard's 20d6 max fireball. Average 62hp of damage, max of 192hp. No there is no metamagic feats for maximizing shit damage.
No Fun Allowed Section: But the running guy has like 1/7th of the mass of the ejected shit, so it should be traveling at 1/7th the speed even with a perfectly elastic impact.
- The bag of holding negates mass for the items inside the bag, and the runner is hitting the back of the bag; laws of inertia are already being ignored before you even open the bag. If you're that upset about it, drop the shit on the wizard from a great height. Fifteen hundred pounds of horseshit is like 375 gallons or 1.7 kilolitres of volume, easily enough to bury someone.
The weight ratio is not the real problem with this use. First, there is the problem of the fragility of the bag itself. Per the rules for this item, if the bag is overloaded or if sharp objects pierce it (from inside or outside), the bag ruptures and is ruined. Per the example above, the running man who is moving at a nice 15 meters per second, does 8d6 damage on impact. Even minimum damage, that is 8 points. Cloth has a hardness of 0 and 2 HP per inch of thickness. That baby is going to tear like tissue and all you'll be left with are some scraps. Second, even if you opened the bag at the listed speed, you would still not get projectile excrement at the same speed. Again, per the rules for this item, if a bag of holding is turned inside out, its contents spill out, unharmed. As was stated earlier, this is magic and the laws of inertia are being ignored. It does not say that its contents spill out at the same speed that it was opened, just that the contents spill out. What is in the bag is motionless and when ejected, is still motionless. It does not gain any inertia from the outside. So, even if you could find a way to protect the bag from destruction, all that would happen is that you would hit the bag and *POOF* run smack into 1500 pounds of bovine bio-waste. Take 8d6 of damage and onlookers will have to make a will save or collapse in laughter at the sight. This is not to say that hurling tons of manure is impossible by the rules, just not with the bag of holding (at least used like this.) You may want to direct your attention to the Shrink Item spell. (Can you say 20 square feet of FLAMING cow shit?)
Commoner, Herald of the End
There is a Flaw- A negative Feat- that turns any Commoner with a Bag of Holding into a scion of death.
Sweet, chicken-y death.
From Dragon #330:
Chicken Infested: You’ve got chickens.Effect: Whenever you draw a weapon or pull an item out of a container, you have a 50% chance of drawing a live chicken instead. No, we don't know where the chickens come from; it's your character.
Let's roll. Sand can be claimed as an improvised weapon. Claiming that one grain of sand is an improvised weapon dealing 0 damage -Which is a stupid claim as anyone has ever tried to pick up a single grain of sand knows so this is where it all falls apart so use a small pebble and claim it as an improvised sling bullet or something- take the Quick Draw feat. You may now take pebble/sand out of the bag as a free action. You can drop the sand as a free action as well. Draw. If it's sand, drop it back in. If it's a chicken, let it go. One can safely say that there are 50,000 grains of sand in a pound, and 1500 pounds of sand in a Bag of Holding. 75 million chickens can thus be produced on the assumption that every grain of sand produces a chicken-which it will in eventuality. If you really want to munchkin it up, use your chicken money to buy a Wand of Shrink Item- create blocks of sand and shrink them- add 4000 times the amount of sand as you crush them to bits. If your DM complains about this, laugh at the foolish fool for letting you get this far.
You now have billions of chickens, each taking up about a quarter cubic foot. Crush your enemies. Crush them all. And then laugh as they bow before you and call you Colonel Sanders.
Something that comes to mind is that, it doesn't say anywhere that the chicken replaced the item you meant to draw. This means that, using only 1 grain of sand or pebble, you can create an infinite number of chickens in an instant and still have your grain of sand. Of course, in that case you don't need a Bag of Holding, so it doesn't really apply to this article.