Eh, I've worked at jobs, before, where 'I'm too drunk to come in' was a perfectly acceptable excuse. But you really have to know your manager(s) for that one to work.

That being said, I'm going to agree with some of the other posters: 99% of the time, your manager doesn't need to know why you're calling out. A simple 'I can't come in today' works just fine. Doesn't matter if it's because of illness, a family emergency, or your cat's birthday. They don't need to know.