I'm kind of an app whore. iTunes is showing 66 apps right now.
Here are my favorites...
Amazon Mobile (nice for tracking packages, easy ordering, etc.)
Assassin's Creed: Altair's Chronicles
Classics (the best book-reading interface I've come across, but unfortunately they don't update the library anymore)
Cogs (fun little steampunk puzzle game)
Comixology (great comic book reader)
Diceworks (another great little steampunk game, this one kind of
Bejewled-edy)
DISH Remote Access (allows me to view TV schedules and remotely set my DISH Network DVR to record)
Dungeon Hunter (great little derivative action RPG hack-'n-slasher)
Earthworm Jim (straight port of the classic 16-bit console game; this is love in app form)
Facebook (loads more quickly than the actual Facebook site for me)
Flashlight. (simple and straightforward)
Google Mobile (pretty much just bookmarks for my Google apps, but effective, nonetheless)
Hanged (interesting little variant on the classic Hangman game)
IMDb (because I am a movie geek)
iSteamTube (another steampunk puzzle game; not as great as the others, but still interesting)
Kindle for iPhone (OMGlove. This is what spurred me to want a Kindle or iPad. I can read again, yay!)
A Masterpiece Collection (very similar to Classics, but it actually updates; great interface, with page turns and little "swish" noises)
The Simpsons Arcade (nice little quasi-remake of the classic beat-'em-up arcade game)
Skype (though I don't use it much, since I've an iPod Touch, which doesn't have a built-in mic)
Stanza (another nice reading app, this one compatible with both e-book vendors and free sources like Project Gutenberg)
SteamPong (take a guess)
SteamPunk Hockey (essentially a steampunk-themed air hockey; 'tis cool)
Twitterrific (for quick Twitter login/reading)
The Weather Channel (quick access to more accurate/detailed weather)
3D Brain ('cause it's just cool)
As soon as I convince myself that I will actually type substantially on the iPod, I'm going to purchase Screenplay.