World of goo is one of my favorites so far. It is a puzzle game where you build stuctures out of little "goo balls" to complete the level. Over the course of the game, you'll realize that the pipes that suck up the remaining goo balls lead them to the "World of Goo Corporation," where you can build a tower into the sky. The Sign Painter leads you through levels, in humorous messages he or she left on wooden signs, or in the digital level, screens.
