Okay, didnt happen to me but others in my old band years ago:
Guitarist: During a solo he ran over and jumped onto the drum riser, which was just 4x8 sheets of plywood set on 5 gallon buckets, with a black fabric skirt around the riser to hide its low-rent construction. The guitarist misjudged his jump and landed with his tips of toes right on the edge of the riser. Immediately his toes slipped off and his shins slammed the corner of the plywood and slid down the edge of the riser, shredding the skin off his shins from his ankles to his knees.
Drummist: Had song where we accented six chords real fast, with the drummer doing cymbal catches on each chord. During these he misjudged a catch and caught a cymbal under his thumbnail, which tore it off. At the time I didnt know this happened because his playing was flawless for the rest of the gig. I would have run home to my mommy.
Singer: He would climb the lighting truss during an extended vamp and swing like Tarzan. One gig he was doing this behind me; I couldnt see him but I could feel the wind from his legs zooming by and see the audiences eyes going back and forth so I just stayed rooted where I was to avoid a collision. However, I felt a huge shock on the stage and saw him wiped out behind me after he had lost his grip. Broke both of his wrists. The casts separated his thumbs from the rest of his fingers and over time it was interesting to see him adapt to using a fork with his index and middle fingers only. He said the worst part was trying to hold toilet paper with those fingers and not use his thumbs.
Another singer, different band: Had a fun coverband that drew flies at a particular club and so there was a tendency to become overserved now and then. During one such occasion the singer noticed the drop ceiling just above the front of the stage was somewhat in reach. Moving the monitors over he jumped up off them to grab the beams that supported the ceiling panels but juuuuuust got the tips of his fingers on the beams, which were only cheap aluminum, and they gave way with his weight. This caused his legs to swing out horizontally as he lost his grip and he fell back-first onto the wedge monitors, breaking a couple ribs. (This was caught on video tape and might be on You Tube, Ill have to check.)
The worst thing that ever happened to me was very stupid and actually happened before the gig, when I was trying to secure a straplock to a strap using a butter knife. Yep; knife slipped off and sliced open my hand, right where the left thumb joins the hand. Dont think those things cant cut! The slice gaped open into an oval shape so I had to go to the hospital and get stitches. By gig time the thumb was still numb from the shots, and by the first chorus of the first song I had blown out all the stitches. It didnt bleed a river but it bled, mixing with sweat to make the neck extra-slippery. Between songs I had my tech wrap duct tape around it but it would only stay on there for a couple songs before slipping off from the blood/sweat and wed have to reapply. After the gig I used my teeth to pull out the remains of the stitches and then just got some butterflies from the drug store and slapped them on there. Today, good as new!