dewster

An odd hybrid of point-and-click adventure game and side-scrolling platformer. It's a combination that doesn't always work, and the gameplay can get tedious at times. But it's also got some great puzzles, a nifty "choose your team" mechanic (a team of three, from seven potential members), and a lot of humor. The story, though, is what I found the most interesting aspect of the game. Each character has his/her own backstory, and they all get the chance to explore that thanks to the metaphysical nature of the titular Cave.

Caveats:
1: There aren't a lot of hours of gameplay here -- even after getting every achievement, I've still only logged about 20 hours. So it may or may not be worth the full $15 asking price for you, but it's definitely recommended for whenever it's on sale.
2: I also encountered a couple freezes and had to replay a pretty significant section of the game to get back to where I was (the auto-save is pretty infrequent), so beware of that as well.