Doggalina
Smash Lord
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It's the WiiWare and PC game that's sweepin' the nation. And it's the best game since Portal, if I do say so myself.
Website: http://2dboy.com/games.php
Trailer: http://www.dailymotion.com/video/k5eG685gIVxEa6NNRc
The premise is pretty simple: Build things out of goo. It's hard to explain in words, so I'll link to the official PC demo:
Steam: http://store.steampowered.com/app/22010/
Non-Steam: http://2dboy.com/2008/10/15/demo-of-world-of-goo-available/
It really is amazing. The visuals are simple yet effective, the music is some of the best I've heard in years, and the gameplay is great physics-based fun. Everybody should at least try out this game, but buying it is worth every penny.
As to which version you should get, the WiiWare version is $15 dollars and has multiplayer, while the PC version is $20 and has more precise controls (due to the mouse).