Any kind, whatever your favorites are.
For news / casual reading, I love Reeder and Instapaper. Pandora's great, of course, but you probably already use that. I use iTap sometimes to control my computer from across the room (as well as Apple's remote app). If you have an iPod touch 4G, check out RedLaser (free) and Pro HDR.
Epicurious is really nice (and free) if you ever like to cook, and PlainText (free), Dropbox (free), and Air Sharing all come in handy. I recently downloaded Calvetica (I have the free "narrow" version) and Simplenote (free), both of which look great.
As for games, I like FlightControl, NinJump, DoodleJump, Real Racing, and Sol Free a lot.
For typing emoticons in text messages and emails, I use Emoji Enabler (which I wrote - it's free).
Last but not least, I recommend Nightstand Central, which I also wrote

It lets you wake up and fall asleep to your iPod music (or even Pandora in the next update), displays your favorite photos, and even comes with a flashlight that you can toggle by shaking your iPod. I use it every night. There are two versions: the $1 full version and a Free lite version.