I've got a Yashica 635 TLR that is still 100% operational. It has been rained on, had hundreds of rolls cranked through it, and once it literally fell off the roof of a car moving at about 25 mph (I just forgot it was up there when I was loading the car). It's never had any maintenance done other than regular use, and a quick visit to the repair shop to have it checked out after the fall (the repair tech didn't find anything wrong with it). So that's my unbreakable camera!

I've also never been able to break a Nikon F or FM2.