So, Zoroastrianism, that's an interesting one. You can make the case that Zoroastrian influence brought into Israel by the Persians was the reason why Judaism became a monotheistic religion and that, by extension, Judaism, Christianity and Islam would never have developed as they did, if at all, without it. It's largely unknown in the west, though. We don't even know if Zoroaster actually existed.
Would anyone like to discuss Zoroastrianism with me?
Anyone?