Fieldrunners
Have an iPhone or iPod Touch? Check out this game that a friend of mine put together with some other folks. It’s called Fieldrunners. It’s an awesome Tower Defense game and is currently getting some incredible ratings from players. They’re updating the heck out of the thing constantly, and I suggest you give it a try! More info (and a video) beyond the break:
Fieldrunners is a game developed by Subatomic Studios, exclusively for the iPhone and iPod Touch platform. Descend into the world of Fieldrunners, the most anticipated and visually stunning game in mobile Tower Defense history! Defend and control the field using a diverse selection of upgradeable towers in a limitless adventure, using a wide array of tactics and strategies against countless waves of unique land and air combatants! Hours of entertainment and replayable challenges! Enjoy a growing experience through free content updates! Do you have what it takes to dominate the fieldrunners and rise to the top as the ultimate Tower Defense master?

Nice, I will check it out today on my iPhone.
Bleh, its $4.99 – do you know if they plan on offering a free demo version of it?