These are my fave apps:
Remote - Control Itunes from your phone
VLC Remote - Handy for changing volume of films when watching them in bed
Shazam - Always usefull when you need to find the name of a son
IM+
Facebook
Simplify - Access music on your itunes on your pc via your iphone wirelessly and be able to stream them. Works anywhere.
AirMouse - Use your phone/ipod as a wireless mouse/keyboard
Jaadu VNC - This is one of the coolest, allows you to remote view and control your pc.
As for games these are my fave:
Bejewled 2
Sonic 1
TNA Wrestling
Assassins Creed
Any of the tap taps
Flick Fishing
Time Crisis
Stick Wars
PEGGLE!