Had this lung going this one time, and I was already pretty ripped. Of course, a lung setup consists of a bowl, the lung, and the lighter. I could not in my high state figure out which to put in which hand, also didn't really give a fuck. So I throw the bowl over to my left hand, and have the lung and lighter both in my right hand. Went to go take the hoot, ended up sticking the still very hot lighter to my face, and caused this terrible lighter top shaped burn. I was quite stoned, so at least it didn't hurt too much.
This other time I was smoking with a few of my friends out by the one guys shed. I was also pretty ripped on this occasion. I took hold of the bong, drew in a fair bit of smoke, then took the bowl out. At this point I realised that I forgot about the handle on the bowl, and grabbed the part that was quite terribly warm. The pain in my fingers started immediately, but I was quite unsure what to do. After all I had a hit there. I didn't want to put the bowl back in and let it go stale, but I also didn't want to burn my goddamn fingers. Another option occurred to me, just throw the damn bowl, but it was pretty snowy outside, and I didn't want to get the bowl wet. So I just sat there with a stupid expression on my face and held the bowl out, like, "Here. Take this." Nobody seemed to want to take it however, and I held it there burning the shit out of my fingers for a good 20 seconds before I came to my senses somewhat. I took the hit then threw the bowl back in the bong. My fingers were quite terribly burned and blistered after this incidence.
I've burned myself countless times getting high, but those were the two most significant.
I also once slammed my finger in a door, then slammed the same finger in the same door the very next day. It bled quite profusely and I lost the fingernail. Those motherfuckers take a long ass time to grow back.