I've actually *really* gotten into a game called
Dungeon Fighter Online. I usually really dislike MMORPG's, but that's what makes this game great--it's an MMO-Arcade style beat-em-up. There's a 1~4-player co-op dungeon mode, and a 1~8 player PVP mode (which I think is the most fun part of the game).
The game is free to play, but the company makes money off of certain items (stat enhancing avatar apparel, in-game shop licenses, health items, etc...)
I'd advise against spending money on it, though, as they really don't give you very much for your buck.
If you do decide to try it out, post your character's name and we can party up.