Gameloft's great looking (and great playing) Halo clone, NOVA, has been recently updated for the iPhone 4. As you may have guessed, the graphics now fully support the wonderful retina display, but the meat of the update is in the control scheme.
With the iPhone 4's new "3-axis gyro", NOVA can now be played with gyroscope accelerometer controls. You will still move around with the joystick, but precise aiming (or impaired aiming... depends on your skill level) can now be done with the accelerometer. Instead of old accelerometer controls though, this one moves 360 degrees and picks up even the slightest of movements.
With the new control scheme, you will play better, but please don't play in public. Check out the video below for Gameloft's own description of the update.