There's a bunhc of free games on the itunes store, mostly demos though. If you like solitaire, you should download Solitaire City Lite v1.31. I don't have an iphone, but i downloaded that game on my sisters iTouch and it rocks.
But to semi answer your question, although most aren't free but follow the above it wont be a problem
Terminal - Use it for SSH Mainly but has other uses
AdBlock - Must Have is a small cost involved but pays for itself - same as firefox add on - less adverts -> faster browsing
App Store Apps
Remote (controls ITunes (yuck yes I know) remotely and does it well)
Jaadu VNC - Best VNC client I have found yet smashes my Windows Mobile PDA VNC program performance wise and just usefulness
iWOL - Wake on LAN client
Warfare.inc - Game I used to use back on Palm OS / Sony Clie / Windows Mobile 5 - very Command and Conquer
Fastlane - Favourite Racing game)
YetiSports - My High school IT lessons summed up in one
Copter - Another IT lesson substitute
Tux Rider - Played it on Linux & Mac
iShift - Strangely Addictive
Heat Pad - Cause its pretty!!
Could go on and on but that's my pick of must have's
Having voices in your head is normal. Listening to them, common. Arguing, acceptable. However, when you lose the argument, you're in trouble.