April Fool's Day is really easy to ignore most of the time. And sometimes the jokes are funny.
As someone who doesn't celebrate religious holidays, my vote is for Easter. The candy isn't as good as other holidays and most things shut down for it, and it seems to be a different day every year, so I always wind up making plans for that day only to realise I can't do anything because everything is closed. No one at work truly realised Sunday was Easter until yesterday and now we have to scramble to get an entire day's work crammed into Friday and Saturday. At least it's a day off, I guess.
Xmas and Thanksgiving at least have enough of a cultural impact that they can't surprise you.
The only 'good' holidays are Halloween and Arbor Day anyways.