What's the biggest F-up you've seen?

I'll start it off with, I was working at a Hilton location, they would bring in CIA students to get their work experience in. I personally showed this guy how to use the hilt of his knife to crack lobster claws and get the meat out. 2 minutes later he is coming to me showing me the guitar chip size break on the blade side of his brand new 10" knife.

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