I don't care much for whining (or whiners) but if something is bad enough I'll bring it to their attention usually with some kind of a joke. In the case of your blood-soaked hamburger bun I'd probably say something like I'm afraid it's going to walk off my plate, could I get one a bit more stationary?
Usually if you do it with humor they'll accommodate. In the rare case where they're rude at me for saying something I will leave no tip.
I had to bite into my bun to find out it was soaked on the underside. Having soggy with blood bread in your mouth is a truly horrendous experience. I thought I was going to heave, the smell alone was appalling. I called the nearest waiter, who turned out to be the manager. He made no argument but didn't apologise either, only offered to replace the meal. I had lost my appetite completely by then and wasn't able to manage to eat that evening, even when I got home. I got a drink on the house to wash the taste out before leaving.
I have never been back since. Complete loss of trust. Not to mention the hygiene dangers of that kind of service. I was in no mood to make jokes about it at the time, I can tell you. I think my companion was quite embarrassed at my outrage and wanted to pay and leave - but there was no way I was going to pay for the privilege of being poisoned. I was quietly spoken, polite, but immovable. The manager had no intention of refunding me to begin with, but eventually conceded.
I have gotten stuff overly rare, or burnt, 2 hours late, completely forgotten, or whatever... these thing are bearable, and not really worthy the time and trouble it takes to make a fuss. I draw the line at eating bread marinated in stale blood though. That's just neglect and willful breach of hygiene standards.
