A Davis P380. Up until that point I'd never shot any auto except my dad's 1911s. Didn't realize you had to keep an eye on the web of your hand. That lesson cost me a good quantity of blood, a nice silk shirt, and the money to get two sutures to keep things closed.
Second worse was also a .380, a Bersa thunder. A peice of the slide broke off while shooting and made a gash under my left eye. Got lucky and that one only needed some steristrips.