I can't believe this hasn't been suggested or featured yet.
Game: Out There Somewhere
Out there somewhere is one of the best games I've played in the past few years, and you guys should definitely check it out.
It's a sidescroller with some great pixel graphics, a very good soundtrack, and a neat 'teleport gun' mechanic which you use to navigate the game's areas. It's unfortunately a very short game, but what's there is very, very good.