My worst restaurant service experience was informing the waitress a bug (a winged ant, at least, so only moderately traumatic on the scale of these things) had crawled out of my lettuce, and having her stare at me rather sullenly for a moment and ask what I wanted her to do about it in an aggrieved tone. And this was a restaurant at which I'd always previously had fantastic service, so it came as a total shock. (After about nine months or so I still wound up going back--their quesadillas are divine--but I've avoided anything with lettuce there since. Never saw her again, either, thank god.)