Friends car blew a radiator hose one day, and of course he had no tools, let alone a spare hose. I walked the shoulder of the really deserted road for a while and found an old V-8 can that looked to be 'bout the right size. Used my Leatherman to remove both ends of the can, and to cut the hose at the break. Slid the can into the ends of the hose, used some wire found in the dirt as a "clamp" on both sides of the cut, poured in some water from our five gallon can (we were on a camping trip, otherwise he would have had no spare water either), and off we went. The patch worked so well he dillydallyed 'bout a month before replacing the hose...

There used to be a story going around about a guy who used a live .22 round as a replacement fuse in his car. Story also said that the round cooked off, the slug (or maybe the case) hitting him where no guy wants to be hit. I don't know if that actually happened or not...