I feel like an app hoarder, I have so many. But, these are the ones I'm most obsessed with:
-Slippery Seal (great new game as addictive as Angry Birds and so cute:
http://itunes.apple.com/us/app/slippery-seal/id499638045?mt=8)
-Scramble with Friends, Words with Friends, Sudoku
-Tripadvisor (I travel and this is a great place to go for hotel reviews, etc)
-ESPN (All the scores, and easy to keep up with games while they are playing)
-Kindle (great for reading)
-News: Zite, CNN, NPR, Flipboard
-Music: Spotify, Pandora, NPR Music
-Movies/TV: Hulu, Netflix
-Productivity: Dropbox, Evernote