Canon 50 f/1.4 Stuck Focus Ring (more in comments)
Last year I dropped my 50 that led me to buy a new one (can't go long without a nifty fify).
Recently I stumbled upon a DIY job that talked about the focus ring being stuck, which is the issue on my old one. So I opened it up, and managed to get the focus ring moving a bit better, but not as clean as I wanted it to. I went back in for another look, and I thought these two things:
1) That inner shaft piece just needs to be bent back into circular shape to ensure the smoothness of focusing.
2) The gears that allow the focusing and all that jazz are just messed to begin with and there really was no hope in fixing it.
I did #1, and it kind of worked. I went to #2, and I failed. I really didn't have anything to lose from doing this, since I haven't touched the lens since last year. On the plus side, I did get a Canon EOS Mount out of this. Saving that for something good.