Here is Imanex with today's instalment of Video Game Things I Never Even Thought Of But Are Very Impressive Now That I've Seen Them.
This is a complete playthrough of the first Portal game, with the catch that the mouse is not moved once to adjust the camera.
What's cool about this is the absolute knowledge it would require of the game and its spaces, since to finish the game like Zoidberg would mean you had to know pretty much every step involved in finishing the game, then be able to trace them back without looking directly at them.
Even if you don't watch the whole thing, do watch the end, where there's some cathartic incinerator action.
Via Game Revolution.