Occult Academy has the greatest anime ending of all time. Period.
Read my posts about it: here and here. They say it all.
But yeah, where Angel Beats confounded me at ever turn, mocking me for daring to think it was any more than a shitty love story that ends happily ever after despite all of the characters being miserable people who only deserved the proverbial “BAD END,” Occult Academy seemed to outguess me and managed to go in almost every direction my insane conspiracy theores went. I totally called for a 12 Monkeys-esque ending and I got it. Awesomeness.