My selection (click for 1440x900 versions, sampled down from 1680x1050)...
GTA IV. This was one that immediately sprang to mind for the comp. I'd played it when it originally came out but GFWL hadn't tracked my achievements so started to play it again recently. Unfortunately, I'd not played enough to unlock the middle island to get a chopper for easier picture taking so had to play for about 3 hours first to get to that point!
ARMA:OA. I only have the demo installed as I don't rate the game, especially when compared to the fantastic Operation Flashpoint (original!) but as OFP looks pretty grim thesedays, I had a play in OA to try and grab something decent. Not the nicest of landscapes but I like the Hueys flying past.
Minecraft. This game takes me over for huge chunks of time every few weeks. One of the things I love about it are the lighting effects, especially when dashing through a cavern, trying to place torches quickly before something nasty spawns! Currently exploring the area pictured (the little stone posts mark cavern entrances) and preparing to make a nice house on the cliff where I took the picture. Still playing my original map!
Miner Wars. I picked this up just before Xmas but only just installed it. Nice to float around asteroids, blasting them! Not yet had chance to explore the gameplay proper.
The last image is the gag one. Hopefully, if I'm lucky I'll be able to get past this red barrier soon!
Hope you like 'em!