Bejeweled, Mahjong, Solitare.
I have others, and some aren't really games per-say... like Armory (BattleNet) and Steam.
I just started Lifeline. Games I have but haven't gotten around to playing yet: FreePlay (Sims), Sudoku, Unblock Me, Tetris Blitz, Peggle, Minions, and something called Pogo Games.