Four clever bits of shade tree engineering come to mind:
1. '76 Civic CVCC, Exhaust pipe broken just upstream of muffler. Cut both ends out of a 3 lb Maxwell House can, cut lengthwise, wraped around the joint, u-clamped both ends. Lasted more than 20K.
2. Same car. Seized caliper. Hung caliper off to the side, and blew one piston out using brakes. Removed from car and beat other piston out. Smoothed corrosion off with crocus cloth. Reassembled with really cheap new pads, bled, and it worked well for about a year, and then seized again. I then fixed it right.
3. Bad injector return line leak on '78 MB 240D while far from home. Went to a handy Meijer, purchase some aqaurium airline tubing, and used to replace leaking injector return line. Got me home.
4. '67 Corona, 1478cc, 78x78mm cyliner dimensions, 2R. Had brakes fail about 250 miles from home. The piston had bottomed out in the master cylider and would not return. Removed master cylinder, went to hardware store. Bought spring intended for use in a door closer, of a suitable diameter. The bore of the master cylinder looked okay and the rubber looked good. Reassembled with door spring in place of orginal, bled brakes (a long process after installing a dry master cylinder), made several serious trials, and was good to go. The car went to the junkyard several years later with the hardware I had installed. Also had to repair the clutch master in this Toy. One of the rubbers from my MGB brake master rebuild kit was a perfect fit for the clutch master of the Toyota.