My personal faves:
1.
Remember the Milk - this along with their
webapp has made me sooo much more productive. It's also the most polished, stable and functional app I've tried to date. Love it.
2.
BeejiveIM - quite simply THE best IM client for the iPhone.
3.
Jaadu VNC - a fantastic, stable & very handy VNC app for remote control of my Mac.
4.
Trails - I've tried virtually all the GPS running/cycling apps out there (iMapMy, Trail Companion, Everytrail, Fitnio, Distance Meter Pro etc.), and this beats all of them by a mile for accurate, reliable GPS tracking of my runs and bike rides. It also integrates beautifully with the Mac desktop app,
TrailRunner.
5.
Gazette - the best and fastest syncing Google Reader client I've seen; use it on a daily basis.
6.
Facebook - not a lot to say, makes me very
unproductive
7.
Touchgrind - I simply
LOVE this game
8.
MobileFiles Pro - from QuickOffice;
THE best document viewer & emailer/iDisk client/spreadsheet editor that I've tried. And I've tried quite a few (AirSharing, OneDisk, Briefcase, Mobile Disk, Files etc.)
9.
Rolando - I had to put this one here. A truly fantastic game, and keeps my 3yr old son occupied for hours!
There are others, but that's the pick of my bunch!