Singleplayer: I'd have to say the Play Your Music (Audiosurf 2, Beat Hazard, and Sounddodger+) games in my collection, as I expand my collection of music. Followed by inMomentum (Honorable mention goes to NFS: Hot Pursuit and Burnout Paradise). Primarily because I like being a lightning-fast ninja, and the overall aesthetic of the game's also relaxing after most of the stress dealt with during the year. With NFS and Burnout, since I've been downgraded to a moped, this makes up for that lacking speed; plus, I can galavant without consequence, and break some traffic laws while at it too while going at skin-rending speeds.
Multiplayer: Speedrunners. Mayhem that's perfect for playing against my siblings with. Unfortunately, I think I'm getting too good at it to the point the game's about the be forbidden from play because I kinda outclass them (almost an Advanced Level by about 100 more ranked points). Fortunately, I'm still on pretty much equal-level against one of them, even in rank; so I'm still challenged a bit. Don't deny the Chicken-Man.
Classic: Unreal Tournament. Against my custom godlikes on godlike difficulty, much ‼fun‼ is always had. Keeps my FPS skills in check, even though I'm almost always last place against them. Only a few times have I mid-ranked against them (out of 9 players, including myself). Starcon: Ur-Quan Masters is a close second, since I'm continuing it at present, and I forget how good it was.
Of course, I'm a tad biased by having a backlog this year, so I have some catching up to do overall.