I climbed with a guy who was alway tinkering with his stuff. Some of his more memorable inventions:
An old nalgene bottle with a hole in the top that tubing fit through to create a hands free drinking system...years before the bladders came out. A binder clip closed off the tube when not drinking. Leaked like hell.
He bought a full on Gore-tex, one piece suit, then glued adhesive non-slip stair tread things to the knees and elbows...in case he had to self arrest they would offer more friction.
A mini picket, bigger than a tent stake, smaller than a picket...good for, well nothing.
Various pieces of home made rock pro including 'hexes' mades from round pipe and T-tonsmade from T stock aluminum.