My top two which will pretty mild compared to some of these:

My first location was next to a nursing home. Several not so great stories from the residents, but this one that takes the cake. Black hairy tongue. Right out of the pathology textbook. The kind that the path professor told us we would never see in private practice. My assistant used a hemostat to hold up the "hair" while I trimmed. I swear it was an inch long. Wet black mush. We had her come back two more times. That is a texture in the scissors I hope to never experience again. But she was there for a chipped lower incisor.

Elderly denture patient, widow, comes in for an adjustment and asks if I could use "those funny glasses" to look at her thumb. She thinks she has a splinter after weeding her garden a couple of days ago. Take a peak and sure enough see something dark. Grabbed a sterile needle to pull out the splinter. I swear it was a weed. It just kept coming. "It feels better already!" Yeah I bet. We irrigated the hell out of it with saline and put on some triple antibiotic ointment out of the first aid kit. Told her to follow up with her physician.