All these Starcraft players, but no LoL? Sad day. Though I did see someone logged in to isotropic as 'HotShotGG' last night which made me chuckle. (For those not in the know, he is one of the top League of Legends players currently competing at Dreamhack in Sweden.)
I used to be kind of serious about Brawl, though never close to good by tourney standards.
I play a lot of rhythm games: GH3, RB2+3, Stepmania, Pump it Up except my local arcade's copy had the screen broken recently :/, Poppin' Music
I recently tried a game of Mansions of Madness, a style of game I had experienced several times with Betrayal at House on the Hill and not enjoyed very much, but to my surprise it was really good! Captured the survival-horror sense pretty well, and had very nice DM mechanics.
I used to be (well, I guess still am?) the best Frames player in the world over at
superdupergames.org, but that was out of about 30 active players XD
I play Magic, but like someone else in this thread, spend more time reading MaRo's articles than playing the game. I think I honestly enjoy actually playing Dominion more than actually playing magic now, though Magic has an amazingly deep system and card set, and I'm even sort of in training to be a judge. I also ran a puzzley magic variant called
2CB at mtgsalvation.com for a year. It was quite successful, and if you have any interest in exploring Magic in a more controlled, nonrandom environment, I recommend checking it and it's sister XCBs out.
And I don't know if this counts as *playing* games exactly, but I spend a lot of time over at
tasvideos.org and have recently begun work on my
very first TAS, of the wonderful
Ninja Senki. If you've never heard of TASes, watch
this (Mario 64) or
this (Pokemon Yellow) and have your mind blown.