Last game I bought was DQV when it was $20 on Amazon.
Hard to say what's next since I get most of my games on sale, and that's not really predictable. Just guessing, it will probably be something during the Steam summer sale, likely Portal 2.
Don't know what the last full game I bought was, but I recently bought the Dies Irae Götterdammerung mini-addon for Hearts of Iron III:
Next game I will buy will probably be Red Dead Redemption, I'd skipped it hoping for a PC release, but since that is unlikely to happen now, I'll just buy it for 360, it'll give me a reason to use the console as something other than a media centre extender.
Last Game I bought was Portal 2. Next will be either be L.A. Noire or InFAMOUS 2 depending on how long The Witcher 2 takes me to finish and what sort of game I'm in the mood for when I finish it.
Found it for $10 at Best Buy when I was looking for inFamous. I'm a Star Wars fan and it was cheap, so I figured why not? It's making for an assuming distraction so far. It's a bit sad they didn't deliver with this actually, I can feel the potential for an incredible game when playing it. Too bad LucasArts botched the concept...twice.
Next game I'll buy would be:
Big Spidey fan, I've heard good things, and it's like $30 now. Time to bite. It will probably be awhile before I buy it though. With The Force Unleashed to get through and inFamous and Stardust HD coming for free, I'll be busy enough.
The last game I bought was Frozen Synapse for the PC.
The next game I buy? Depends on when I have a working 360 + Gamertag again. LA Noire if nothing I wanted on XBLA is out by that point. More than likely though, it's going to be one of the 50 billion XBLA games in the pipeline I'm looking forward to.