Bubble Tanks Tower Defense JAN 19 2010
I didn't think much of this one at first (yet another tower defense game, right?) but the megatower wrinkle helps make Bubble Tanks Tower Defense almost unputdownable.
Oh, and there's a level with unlimited money to spend on towers and upgrades to defend against unlimited enemies (it's the last board in the top row). I built up the board as much as I could and let it run overnight. After 10 hours or so, the game got to level 2758 before all 20 lives were gone.