iPhoneAssassin is a meshing of a social game and iPhone geekyness.  The site says: iPhone Assassin is a game for iPhone users where you virtually "assassinate" other iPhone users.
To play, first sign up by pressing JOIN at the main page at iPhoneAssassin.com. This will give you your special code name, consisting of three letters and a number, such as "Alpha Bravo Charlie 1" or "ABC1".
Next, click on the "Set your nickname" link to create a nickname, like "Joe the Assassin".
Now, go and find someone else with an iPhone. Show them your iPhone and tell them "This is an iPhone Assassination!" Then, tell them to use the iPhone Safari browser to go to iPhoneAssassin.com so they can join the game.

I have to admit I only 'assassinated' people in my office and they looked rather confused...but I still think this is a good idea. 

Poke the smileys and make them go away...another game from myHip that's just like many others from them.  Not the most amazing game but if you're bored and want to waste 5 minutes this works. 

There are a lot of higher quality games out there though. 

Cellufun is at it again and this time it's with a great game that's similar to the old school Atari games.  Their website says:

Wave after wave of marauding ships intent on your destruction appear in formation above you. Defeat them all only to confront their increasingly difficult boss ships. 10 challenging levels, 3 bosses, and a slew of power-ups await you in this space shooter reminiscent of Space Invaders and Galaga.

I definitely enjoyed Attack of the Zloggs.  If you've ever played Space Invaders you'll love this. 

This is pretty much Bejeweled without the razzle dazzle. Match the colors and get rid of the rows. 

You'll start out with two colors making the first level very easy but as the levels go on it becomes more difficult.  Overall, I like the simplicity of Avalanche.  It's easy to understand and play.