Threes! This is my new iOS crush. Its a great puzzle game. iPhone and iPad both. $1.99. Just a fantastic game Its got a great user experience and minimalist design (a la Letter Press). You should get it. You won't be disappointed.
Proteus by Ed Key and David Kanaga, for Mac/PC/Linux, is a game that is all about the experience of exploration and discovery. I can't shut up about how much I enjoy this game. It's wonderful, and definitely not a typical game play experience.