Snakes and all other poisonous (particularly venomous) animals except the platypus.
Everyone, everywhere, that has ever sincerely used any of the following phrases:
- that's good enough
- that'll never happen, don't worry about it
- who's gonna know?
- i'll be retired before anyone finds out
- i suppose we can make an exception just this one time
- it's always been done that way, i don't care what the rules say
- i don't care about data integrity, i just want to do my job
- flat files are just as good as a relational database