I said at the end of my Games of 2011 post that I knew I had forgotten some games I played. Here are two:

Pushmo - The first must-have on the Nintendo 3DS's eShop, this is easily my favorite puzzle game of the year (and favorite in a while). The game mechanism starts simple but ramps up in difficulty very quickly. It also uses the 3D to great effect, the game becoming easier when you have the effect turned on. If you have a 3DS this is easily worth the money. (And I have to reiterate that Super Mario 3D Land is worth the system alone--so go buy one.)
The Binding of Isaac - For Windows/Mac, this is an interesting one-man game. The story is really morbid and the art is downright creepy, but the game play is fun. You basically go through randomly generated dungeons picking up random powerups (from an absolutely enormous list). With inspiration pulled from the original Zelda and rogue-likes, but with keyboard control similar to dual-stick shooters (think Geometry Wars and Stardust HD) it's worth the cheap purchase price if you like playing games that are different every attempt in order to collect oodles of things and can handle a bit of blasphemy.

Now I still suspect, but am not sure, there are still more.