My top five:
1) Sand blasting a part, then mistaking a can of WD40 as my primer.
2) Standing on a 5” cheater bar to “loosen” lug nuts on the left side of the HT only to twist the stud off. “Lefty tighty, righty loosey”
3) Not knowing there is more than one guy on the planet selling parts (computer stupid).
4) Grabbing old cracked plug wires while it’s running.
5) Buying a part again because I forgot I had already bought it a few years earlier (who needs an air horn clamp?)