I was doing incline dp presses in high school and my workout partner left his db on the floor. When I got done with my set, I lowered them pretty fast and sandwiched my finger between the two db's, splitting my finger wide open and needing stiches. Another time in hs, I was squating below parallel, lost my ballance and fell back. Didn't know it at the time but I had my knuckle inside the holes in the power rack and when I stood up, I ripped the skin off. Still can see the half circle scar 23 years later.