From 1d4chan
Genasi and Elven Swordmage

Swordmages are mages with swords. Basically, take a kid who realized he wanted to be a fighter when he grew up, then learned he was too weak to properly kill a monster with his sword. So he lit his sword on fire or hooked a car battery to it, and now boom! He's in business.

Introduced in the Forgotten Realms Player's Guide, this is the first (and only) Arcane Defender using pre-Essentials design principles. This class probably originated from Eladrin, which is weird since Eladrins aren't necessarily the best race for Swordmages compared to, say, a Githyanki, but then again who cares, Githyanki don't even have feat support like a core race. That said, Swordmages decided that since they're good at magic but not really that strong, they'd just cast spells and inscribe runes onto their sword and use it to stab foes like a magical syringe full of TNT. Their class features allow them to benefit from using a one-handed sword without a shield to marginally make up for their lack of shield and heavy armor proficiency. They also have potent feature powers for marking enemies, so that if they attack the Swordmage's allies, he can do something magical that assists that ally.

In fact, the swordmage's "subclasses" stem from this protective feature. Called the Swordmage Aegis, the different responses different the different types of swordmage; those with the Aegis of Assault (FRPG) teleport to the assailant and make a free attack, whilst those with the Aegis of Shielding (FRPG) reduce some of the damage that their ally takes, and those with the Aegis of Ensnarement (Arcane Power) can instead teleport the attacker to them and make them more vulnerable to their imminent ass-beating.

Unfortunately for Swordmages, their third class feature doesn't actually confer a significant benefit in combat - Swordbond, which allows them to pick a weapon with which to bond. They can rebuild the sword if it is broken with magic, or they can summon it to their hand if it is within a certain distance (which is reasonably far.) No powers of theirs really take advantage of this (unless somehow their thrown sword power is botched and they need to get their weapon back pronto) but it can be useful if you find yourself disarmed in some lame gladiator/prison scene. It can also turn up profit: simply sell your sword, then when safely in possession of the coin and away from the merchant, summon it back into your hand. This is a great way to convince a DM to kill you, though. Another thing you could do, is use your sword as a trap. Hide it in a bush, put your target between you and the bush, then summon your sword to your 'hand' impaling the guy in between you and the sword.

The Swordmage actually isn't an entirely new creation for 4th edition; it traces its lineage back to the AD&D Forgotten Realms racial sourcebook for elves, where as part of the vast amount of overpowered cheese elves got was a race-restricted Fighter/Wizard kit called the Bladesinger. They were promptly shoved under a rock and buried with as much of the embarrassing shit from that book as possible, the theme lived on in first a prestige class, and then the Eldritch Knight, and then the Duskblade of 3rd edition. In 5th edition, the Bladesinger came back as a wizard tradition, and some of the Swordmage's spells were brought back, now being shared by wizards, Sorcerers and Warlocks.

Swordmages have a number of Paragon Paths outside of those found in the Forgotten Realms documentation, such as the ones in Arcane Power as well as one or two tucked away in the Manual of the Planes. Most Swordmages take the "Intelligent Blademaster" feat, which allows them to use their Intelligence modifier for melee basic attacks and opportunity attacks, instead of their strength.

Those players who are fans of gishes are conflicted on the Swordmage. On the one hand, it is without a doubt the purest invocation of the "feel" of the gish, with every power and feature reinforcing the idea of a warrior-wizard who attacks with sword and spell simultaneously, all without overshadowing the rest of the party or making either fighter or wizard obsolete. On the other hand, it's a 4e class, so it's tainted by that negative reputation which 4e has.

And then, of course, there are those who insist that the ability to do things like throw your sword so that it stabs some fucker in the chest and then blows up in a fireball before reforming in your hand, turn your sword into a lightning bolt that bounces off of multiple targets, cut doorways in space or split yourself into multiple copies who can each fight independently is not gishy fucking awesome.

Dungeons & Dragons 4th Edition Classes
Player's Handbook 1: Cleric - Fighter - Paladin - Ranger - Rogue - Warlock - Warlord - Wizard
Player's Handbook 2: Avenger - Barbarian - Bard - Druid - Invoker - Shaman - Sorcerer - Warden
Player's Handbook 3: Ardent - Battlemind - Monk - Psion - Runepriest - Seeker
Heroes of X: Blackguard - Binder - Cavalier - Elementalist - Hexblade - Hunter
Mage - Knight - Protector - Scout - Sentinel - Skald - Slayer - Sha'ir - Thief
Vampire - Warpriest - Witch
Settings Book: Artificer - Bladesinger - Swordmage
Dragon Magazine: Assassin
Others: Paragon Path - Epic Destiny