Seconding Braid and World of Goo, both quite unique in the world of games, music, art, etc. Cool experiences. Wife liked World of Goo too, which was a surprise, though she hasn't tried Braid yet. Both run on my gimpy laptop which is a big plus.
Braid has me totally stumped on level 2, which is embarrassing, but it's cool you can traverse the whole game without having to actually beat every level. Cuts down on frustration. Kinda like taking a test, then going back to the ones you couldn't figure out the first time.