All Hallow's Eve
Halloween can't really be called a holiday, for the simple reason it's not one, not any more, though it has its roots in an ancient gaelic festival (http://en.wikipedia.org/wiki/Halloween). All the trappings of halloween, children dressing up as ghosts and goblins, the giving out of candy and other goodies, the symbolism of black cats, jack o' lanterns, and witches, even bobbing for apples, have very specific origins. Sadly, they're all lost to us, just the way we've lost the true origins of almost all our holidays, leaving us with nothing but marketing opportunities. Meanwhile, I have a nagging suspicion that kids can't enjoy halloween the way we once did because it's been taken away from them, preempted by closeted cross dressers.