I once found a chewed on cap of a blue bic ballpoint pen in a soft chicken taco at Taco Cabana. Eh, it's Taco Cabana so I did nothing about it, but did not finish lunch.
When I was younger, I looked really young and pretty much every time I went to a decent restaurant I had the worst service. I figured the staff looked at me and figured no "no way that kid will tip well" which was quite the opposite and put me in a position where if I got bad service and did not tip well they would think they were right. I almost always overtip, especially if it a place I frequent. So anyway, I was about 22 or 23 and eating a small, decent seafood place in a CT shore town. I was by no means a regular, but would do about 3-4 dinners there a year for special occasions, dates, whatever. One time, we got the worst service ever. Just terrible, things like never got bread or our salads, waitress never came by and asked if we needed new drinks, when they brought our meals and we mentioned the salads, she ended up bringing them after we were half way into our meals and squeezed them onto the table, which was the last time we saw her until she brought the check. Ended up finishing the meal without drinks, they never cleared our plates, asked if we wanted coffee or dessert, nothing. Just brought the check after we had sat there with dirty plates in front of us for 30 minutes. I could not not let this one go. No way I was dropping my customary 25% on the bottom line for that service, so I give about 10% and ask to see the manager when we are retrieving our coats from the coat check. Manager comes over and I explain everything (way more than I have explained here since it was more than 25 years ago and some of the details escape me) and why I did not give a large tip and that I was extremely disappointed in the service that was so poor. So the manager just says, "she was probably just having a bad day, it can happen to anyone." So I explain that she did not seem to be having a bad day for the other tables that actually ended up having dessert, and the manager just said "oh well, we hope you will give us another chance." Well, I hold a grudge and would never go back there ever again. Fast forward about a year or two and I am at a friend's house a few blocks from the restaurant. I know the family is friends with the owner and he happens to be at their house, so I tell him I had enjoyed his restaurant for years, food was always great, but the last time I was there, the service was so bad and what the manager said, and that I did not think I'd ever go back. He just says, "well, sorry to hear that". Place burned down a few years ago and I am not sure if it reopened, but I never went back.