I haven't had any since I started working at the library, but I worked in customer service for twelve years and completely lost faith in the intelligence of the human race in that time.
While I was working at a coffee shop, I had a customer tell one of my coworkers she was a F***ing idiot because the eclair she was going to order got sold before she could order it.
While I was working at a bookstore, a man threw an item he had bought and was trying to return at my coworker's face because she wouldn't take it back (it had been removed from it's packaging, didn't have all the pieces, and was past the return policy).
At this same bookstore, I was putting some books back on the shelves and came upon two kids (they couldn't have been older than thirteen) in the middle of a blowjob.
Bookstore again, I went to the bathroom and found two people in one of the stalls doing...um...stuff.
Final bookstore story (although there are many), and probably my favourite: I had only been working there for a week or so, and was walking up the main aisle tidying the display tables. I was straightening a pile of books, when out of the corner of my eye I see a bare bum...seriously, I kid you not. A group of boys (who were obviously stoned) were walking up the main aisle, one of them with his pants down past his knees, the others videotaping his actions...and this was maybe two weeks before Christmas, so the store was PACKED.
Oh the fun of customer service...