I'll admit it, I have a bit of a iPhone addiction. So I go through an unhealthy number of games on my phone every week. Often they lose my interest after a day or two.
But I'm quite captivated with WordFu, a blending of Yahtzee and Scrabble with a few power-ups and plenty of silly sound effects thrown in for good measure.
To play you shake your iPhone to scramble the letter dice. Once you're happy with your selection you touch play and start touching out the letters to form words. The more words you form the higher your score.
If you form enough words you start getting power ups that do things like freeze the time, let you change out a letter die or gives you a score multiplier. It's a simple concept, but quite a bit of fun.
The only downside is that there's no online support, just local multiplayer, but it's only $1, so I'll put up with that..