I've got the 2 best timewasters on my phone; Red Mercury's Acid Solitaire and Freeverse's Flick Fishing. I've been a big fan of the Acid Solitaire game since I first installed it on my ancient Palm Pilot with its black & white screen several years ago- heck its the only reason I kept the Palm around was for that game. The iPhone version is a huge improvement over the previous version, has beautiful color and addicting play action.
And the Flick Fishing game is the most addicting 99 cents I've ever spent! It's huge fun, intuitive and colorful. I just added this game to my phone for a few days but it is quickly wrestling my playtime away from the Solitaire game. If you have and iPhone- go get it before the price jumps up!