It's not controversial in the context of historic and orthodox Christian thought, but here on CF and for a lot of modern--especially Evangelical--Christians the hope that ultimately all might be saved is certainly controversial. Note that I'm not a Universalist, I don't believe all will be saved; but I do earnestly hope and pray that, ultimately, all will have life with God in the Age to Come. It is hope, not dogma.
If not that, then the most controversial theology I hold to is basic Lutheranism, especially the doctrine that we are saved by grace alone through faith on Christ's account alone. We get funny looks from Calvinists and Arminians; we get funny looks from Catholics and other Protestants. Catholics usually think we're just another form of Protestantism, and Protestants usually think we're basically just Catholics. So if you're looking to be weird and have nobody know exactly what it is you believe, Lutheran is a good way to go. We also seem to get along pretty well with Orthodox, perhaps because we share with the Orthodox an appreciation for mystery and paradox--or maybe it's because the Orthodox are also considered weird, at least here in the West; so we end up being weird together.
-CryptoLutheran