I'm a Pinhead
You guys know I talk about how important good lenses are, right? Like all the time. Well take a look at this picture and see if you can tell me what kind of glass I used...
Ah ha, trick question. I used no glass at all. I took that photograph with a pinhole camera. Or rather, a modified body cap on my 5DII.
Basically you drill a hole in the middle of a body cap. Then cover the hole on the inside of the cap with a piece of foil. Then make as small of a hole as you can in the middle of the foil with a pin. Stick it on your camera and shoot.
This is actually the most simple a lens can possibly get. Basically it goes all the way back to the camera obscura.
Here are more detailed instructions for and a much better built example of what I did. The smaller and more perfectly you make the hole the foil the better, but I just played until it worked. Actually I found those instructions after I had, through a number of lesser iterations, come to the same configuration myself independantly. Like I said though, his is much better.
I'm certainly not going to give up my L glass, but it was fun to experiment for an hour or so.