Run and/or play
Burning Wheel: I've been curious about this game since I heard about it on the Sons of Kryos back in the day, and I'm even more anxious to try it out now that I have the books. I have a couple of settings I really like in mind, and I love the lifepath character creation system.
Pathfinder RPG: 3e was my introduction to D&D, and this seems like what I've had a huge amount of fun with over the years with even more options tossed in. It's even more complicated in some ways, and the power level has definitely gone up, but it seems like tremendous fun.
Spirit of the Century: I borrowed a copy of this from my GM a while back, and I must say, I'm impressed with the FATE system. It looks like it's fast, slick, and tremendous fun.
Dogs in the Vineyard: I love the idea of teenage witch hunter gunslingers. The Situation of the game seems so cool. I got bitten by the mechanics in a previous Vincent Baker game I played, though. Good and careful planning, it seems, is no match for the fickle hand of fate in In a Wicked Age.
Play Only
Mouse Guard: I have no confidence as a GM in someone else's precreated setting, but this seems like such enormous fun. Plus I love how noble and courageous the little mice are.
Dungeons & Dragons 4th Edition: Sounds fun, but I am not buying it, at least not until I reach a higher income level. My 3.0/3.5/d20 collection fills an entire bookcase.
Run Only
Mutands & Masterminds: Now that I've played it, I'd love to give running it a try.