There's also Tilt To Live. Not sure if it's on anything other than iOS, but it's a simple game where you have to guide your arrow in a box-arena avoiding red dots. You destroy the dots by navigating your way to various power-ups. Keep the kills going for massive combos and aim for high score. If you get touched by a dot, you die. Sessions can last a few seconds or a few minutes depending on how intense you get into it. Pretty good fun! You might look a bit silly though on the bus trying to move your arms to tilt it though.
I shouldn't forget Doodle Jump either. Incredibly addicting, you have to tilt the device so that your automatically jumping character can safely land on the next highest platform. Avoid monsters, get power-ups to boost your height. Simple and effective.