Portal
I played Portal, which is part of the Orange Box game package. It was original, funny and entertaining. I couldn't resist posting two youtube clips. Here is a pre-release clip that shows how the game works and gives you an idea of they type of problems you'll solve. It also gives you a hint regarding the types of puzzles you'll solve. This second clip has a spoilers, it's the end game movie and 'song' that's played after the game. If you haven't played I'd wait. (How weird is it that I like to listen to this while programming at work.) At the end, there will be cake.