Aside from the nipple rash and quite a few bruises from landing on my board the wrong way, the worst was walking out on the west side of Santa Cruz.
One of those west of Steamer Lane outcroppings of rock covered with mussels. Was low tide afternoon in winter IIRC, so more steps than normally necessary to get off. Sliced my heel really good on the walk out. Felt it happen (must have been razor sharp, this one) but didn't "hurt." Noticed a pool of red under my feet in the water. Was only me and a couple other guys out so I kept surfing into the sunset cuz the bleeding stopped right away. No one noticed any chum, so, fvvk it. Got out and bleeding started again, pretty bad. Hurt like a motherfooker too by the time I was dressed. Wrapped it in a towel.
Couple/three days later I was getting my vasectomy and the urology nurse noticed my foot wrapped up, then took a look. She said it had begun healing and stitches, while maybe would have helped two/three days ago, were unnecessary at this point. She sent me off with a bunch of dressing and antibiotics for it, and sore nuts.
Oh, that and going left (backside) and landing on Waiohai Reef and tearing my back up a bit.
Worst I ever saw was a guy whose pointy nose went through his upper lip at Steamer Lane. That was gross.