Jupiter Lander
Jupiter Lander is a clone of Lunar Lander written in 1981 by HAL Laboratory and published by Commodore. Apparently Eidos Mobile has ported it to J2ME phones, and the wikipedia article on Lunar Lander mentions Jupiter Lander being released for Amiga as well.
Concept
This is a straight-up clone of Lunar Lander; you control three thrusters (one down, one left, one right) to fight gravity and attempt to land a space module on a craggy surface. The action is in 2D, and only the landing pads are safe to touch. You need to control both your speed and position to successfully land.
Places to Buy
Look for Jupiter Lander on your favorite VIC-20 or Commodore 64 ROM site.