Try Belowscape. It's awesome! Fast paced action game for iPhone and iPod Touch inspired by Robotron, Smash TV, Crimsonland, and Geometry Wars. Tilt the device to move. Lay it flat to not move. Touch the screen to change the firing direction.
"This one is golden waiting to fill the gap in your library."
I now consider this game a must-have
"Excellent Control Methods with Plenty of Options, Attractive Look & Style, Online Leaderboards"