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Seriously, this is the best idea ever:

Basically, you're a razor, and you have to run through a number of increasingly weird 3D levels, chasing cats, and shaving their balls. The cats get increasingly hard to find, and there are an amazing number of them. There are tabbies, tortoise-shells, Siamese, and cougars. As you complete levels the razor gets more powerful and you have to be careful not to hurt the cats or neuter them. When you succeed in shaving a cat's balls, it spits up a diamond that you can collect.

As seen at Crooked Timber.