Oh boy, I've seen a few:

• At a startup, one dude had obviously lied about his credentials. He was hired as a writer, but couldn't write shit. He spent the entire day hitting on women and bitching about how his ex wanted support for a child he wasn't convinced was his. He was fired about 3 days in...

• When I was a student, I worked at a sports store. One girl there was, let's say, packing in the chest compartment. She was also about 17, maybe 18. Most people were nice enough to not hit on her, but one day the security guard (who was maybe late thirties at the youngest) made a comment to me to say "I would absolutely destroy her back door, you know?" (but slightly more graphic). I told management, and she was brought in. She broke down, and went over all the off-hand comments he'd made to her. The manager immediately walked out, told him he was fired, and apologised to her.

• An old employer hired this guy who was a Microsoft MVP nominee. The guy was one of those types that could talk brilliantly, but couldn't take criticism. He listened to me, as I was senior, but ignored anything from managers or people at his level. To cut a long story short (I could write a book on this guy, and it would be hilarious) he lied about a project he worked on solo for six months. After checking in on his work we found he had bypassed our PR system and had been accepting all of his own requests, so no one has verified his code. It was an absolute mess. It cost the company a quarter of a million, for a project that should have brought in £50k. We later found out he was a nominee because he was so active on some Microsoft support forums, and mostly got that through posting "yeah I had the same problem" or from supplying easy or wrong answers. That loophole was closed shortly after...