I don't have any Macguyver-isms to do with hiking, but I do know a lot about field-expedient vehicle repairs, since I own a Jeep and offroad it a lot.

Lost brake fluid reservoir cap? Ziplock bag and electrical tape will allow it to keep pressure.

Starter problems? Jump across terminals on starter with a screwdriver or pair of pliers.

Broken brake line on one corner? Roll the line on itself a few times and pinch it off with vice grips to keep all the brake fluid from leaking out.

Tire came off the bead? Spray carb cleaner inside tire and light with a match (EXERCISE CAUTION IF DOING THIS) then re-inflate tire.

Wheel broken off at the studs? Build a skid out of a log and some rope or ratchet straps.

Snapped axle shaft allowing axle to fall out? Ratchet-strap a tree to frame and back bumper to keep it in, de-bark tree and smear grease or oil on it where it will be rubbing against the tire to cut down on friction.

Need an improvised bucket? Open ammo can. Improvised jackstand? Closed ammo can. (those son-of-a-guns are TOUGH)

Need to get a tire OFF the bead to repair it? Place tire underneath vehicle, place your jack on the tire right next to the bead, and jack up to the frame or bumper. This will push down on the tire and break it off the bead.

Bent tierod? Pull it off, bend it back as straight as you can get it by whacking it on a tree or big rock, and sleeve it with a jack handle or length of pipe, then re-install it.

I'd have to think a little, but I've got more. I've had to do a lot of crazy stuff to limp broken vehicles out of the woods. I carry more tools than a Snap-On truck, and a bag full of ratchet straps and bungees, zipties, duct tape, electrical tape, you name it.