I'd love to get my hand on some of the "new" hit games, like Left 4 Dead, Saint's Row 2/ Grand Theft Auto IV, Dead Space and Tales of Vesperia just to name a few...
I've just started getting into the Dragon Quest games so I'd love to get some of the others in the series, and I still need to get Kingdom Hearts RE: Chain of Memories as well.
I've been waiting to pick up Batman: Arkham Asylum, Dead Space, and Call of Duty 4, used for the 360.
Batman and CoD4's prices don't move very much, so they'll be a while.
I would love to boost my 360 collection with some huge titles that I have missed over the years. Maybe I'll try Gears or even *shudder* Halo
I also would love to pick up some last gen games before they run out of them
Mostly anything I would want to get from them would be PS2 games.
But I guess I can do with getting games that don't usually have any good deals going for them (namely PS3 games). Hevenly Sword and Eternal Sonata to name some.
Fable 2, Little Big Planet, and Heavenly Sword, especially Little Big Planet and Heavenly Sword since those are still almost full price when brand new.