Just to throw in my 2cents with the make-your-own tools section:
It's basic, and every shop mechanic probably has dozens, but my favorite home-made tool is to take a broken or old spoke and grind one end to a sharp point. Great for opening brake cable housing, pushing bearings around, scratching marks for cutting, poking people, etc.
The other is to take a short (2-3 inches) piece of brake cable housing and add ferrules at each end, to use as an extension for a 3-rd hand tool in tight spaces.