Let's just all assume the first answer is SK :)
What are you playing right now? I just finished Portal 2, it was fun but got a little repetitive for me.
I picked up Might and Magic: Clash of Heroes for XBLA and it's fantastic. If you dig competitive puzzlers, this one is for you.
I also continue to play a little Nightmare of Druaga when I can. It's a pretty obscure rogue-like with a really interesting turn order feature where monsters are color coded according to their speed. SK takes a great deal of inspiration from rogue-likes, so I never turn one down as there might be an interesting nugget in there worth exploring.
I liked M&M:CoH before it was popular. So HA!
No, seriously. It's got just the right amount of puzzle RPG and random elements in the mix (compared to, say, Puzzle Quest which is ALL RANDOM, ALL THE TME).
The other game besides SK I play right now is Alteil. As far as deck building card games go, it's pretty much the best I ever played.