If you haven’t heard of World of Goo, what rock have you been hiding under? It’s one of the greatest Physics based indie games ever. To celebrate 1 year of release, the developers have a special sale going on at their homepage that you really should check out: http://www.2dboy.com/games.php It allows you to pay whatever you want for a copy of their game!
There have been some pretty crazy estimates that 80%+ of the copies of their game has been pirated. If you are one of those, here is a chance to make yourselves feel better. You can pay as little as $.01 but give them a few dollars and let them keep developing games. Currently the site is being hammered so if it doesn’t work right away, give it a few hours. The sale is supposed to be on for a week.
If you don’t own this game already, you really should head on over to the site. World of Goo is an absolute classic!