1# "Sorry, we don't allow pets here"
2# Child and animal abusers
3# People who are rude for no reason
4# Unmitigated greed and averous
5# People who lack compassion
6# People who tell you it's "all in your head"
7# People who try to act tough and give you "the stare"
8# Automatically being judged by others before they get a chance to really know you
9# Spammers and telemarketers!!!

I'm sure I could think of more...