Dungeon Defenders.
It was on sale on Steam the other day for like $2/copy, and hopy shit that game is so freaking fun.
It's pretty simple ... It's a castle defense game, but you pick a hero character, and play as them in a semi-hack-n-slash role, where, when you build up enough mana, you can summon other defenses to help you out.
Your heroes level up, and mobs drop new equipment that you can either equip, sell, or improve. You can also get pets to help you out and other fun little nifty items.
The best part is that you can play online cooperatively, in either a private match you set up, or in any other online game. You can have up to 3 other friends help you on missions. And sometimes they can get pretty damn hard!
Anyway, what an unexpected gem! The art is adorable--looks a lot like WoW graphics. The animations are smooth, and the levels are varied and nicely designed.
It can be hard to start on, b/c it doesn't do a great job of explaining what things do, but outside of that, I have no complaints really. EXTREMELY worth the money, even at full price :D
I've got a Huntress and a Countess character ... My Countess is a fucking GOLDEN GOD who can only be damaged by the mightiest of bosses, and does like 4000 DPS at lv 29 :x
In one battle, I fought an Ogre & killed it single-handedly, while being hit on all sides by those exploding Kobolds & the Orcs etc. On hard :x
That was so awesome :D
Though if you want to do the MOST damage overall, you have to go for a Huntress-type trap-laying hero. And for the most kills & MVP status, every freaking time, go Apprentice or Mage. Their defenses they build are stupid ridiculous. Monks are sort of balanced and are excellent supportive chars.