Links just as much for you, as me so I don't lose them. I highly recommend all of these.
KnightfallKnightfall 2Puzzle games where you rotate the board, destroy matches, and position your knight to kill any non-block he falls onto. Excellent quality. Knightfall 2 has a neverending dungeon in it.
Kingdom RushTower defense of excellent quality too. About a dozen levels, challenges and rewards to increase replayability. Tech trees. Boss fights and zones that are more than "big slow monster".
Dice WarsThis doesn't have the polish of the others, but it's fun to play for 2 minutes at a time. It was redesigned somewhere to add multiplayer functionality. It's essentially risk with random worlds and very stripped down gameplay.