He is credited with banishing snakes from Ireland, but modern biologists are pretty sure that post-Ice Age Erie has always been snake-free. He also has a bell, which is part of his shrine and his iconography (It's pretty!).
So, raise a whiskey to the good saint and remember to invoke him against snakes and witchcraft (unless, of course, you like snakes and witchcraft - in which case, Fie! on Saint Patrick!)