Probably just my ineptitude, but whenever I worked on cars when I was younger, pretty much always ended up cutting or skinning myself.
I think my worst was whilst doing some minor work one evening under a car. Was using a lead-lamp. Stood up to go back in the house, but was basically blind because of the lamp. Tried walking through the front door hole, missed by a metre, and broke my nose hard enough to heard in the kitchen.