I was researching new lenses for my 7D today and decided to try it without one.
With some cardboard, tin foil and a little tape, I had a pinhole video camera!
I'm still working on just the right size of pinhole. Too wide, and it's far too soft, too small and you need so much light you have to work at 3200 iso in broad daylight! I'm eager to try this on a 5D MK2 and take advantage of it's sensor.
I love the lens flare (sensor flare?) that I got, and the vignette on the black and white shot at the end.
ISO 3200 (1250 B&W shot)