I had one of those plastic clip-on cases for my phone and it was really on its last legs - corners broken off, splits, etc. The screen had come in for a bit of abuse as well and the screen protector actually came off in my pocket! (You can see the remains of the old case in there, my camera is my phone so I couldn't take a pic of it in situ!)
So I decided to make myself a belt case for it so it wouldn't get so damaged, and this is the result. I worked out the rough pattern by simply wrapping a piece of paper around and working out the max dimensions. I then started cutting up bits of paper to figure what shape I wanted before making a card template. The leather is some I'd got for other projects. Design and build was over 2 days, with the pattern I could probably knock one out in half an hour.