I have so enjoyed this thread, and have a few of my own:
Two different locations of well known Italian chain have waited 45 minutes between collecting mains plates and asking if we wanted anything else.
Another Italian chain had left a massive barnacle in my seafood linguine which I then bit down on. Still feel a bit sick thinking about it.
Had a weird experience with a waitress at another place. Went there with DD (who was about 5 at the time) and we placed a drinks order. I ordered orange juice and she kept on at me to order alcohol. I said I was driving and wouldn't drink with DD there anyway and still she kept on. She said "What, are you a child too?"
She then hassled me when I ordered a pizza, trying to get me to have other things. When we'd finished our mains she took DD's dessert order whilst asking if I wanted to see the dessert menu (thought this was odd in itself). She then brought DD's dessert, dessert menu for me and disappeared for half an hour, by which time DD had long since finished and was very restless. She came back to ask what I wanted and seemed most affronted when I said I wouldn't have one.
Another place DD found chunks of plastic in her ice cream. They were very apologetic and took that off the bill (I should think so!).
Most recent one was in a dessert/ice cream parlour where I overheard an argument between horrible man and the manager. Basically, horrible man's wife had ordered the wrong thing for him, which had then been served. He wanted the difference in price deducted from the bill, which they were unwilling to do. He was just so shouty and his kids were in tears. His wife was trying to say it was her fault and he kept telling her to shut up. He then made racist comments to the manager along the lines of going back to his own country, despite the fact that the manager was clearly from Birmingham. Just awful to hear, and the language!