If you want a quick, free iPhone application to show off the cool new motion sensors in the iPhone 2.0 software, then download iPint.
It's not a game that will keep you hooked for weeks - indeed it's just excellent viral advertising for Carling lager - but it's amusing enough to make friends and family goggle a bit and maybe look at their own puny phones with scorn.
You have to slide a pint of lager along a bar, missing various objects and without letting the full pint smash to the floor. There are three levels of difficulty (Beginner is a LOT easier than the others!) on different bar surfaces.
When your pint is safely in the hands of the customer at the other end of the bar, you get to fill your own glass with lager, and as you tilt it as though drinking from your iPhone, the liquid drains away.
Due to its rather obvious alcohol reference, you have to be aged 17 or older to download this game.
It might encourage binge drinking for the first few days you have it on your iPhone, but it's such a neat little amusement that its going to be shown off and played with many times as new people are shown this little wonder.