I found this list that puts the dubs up there with some of the greats.
I'm sure Satan came up with these other religions just to make the one true religion harder to find.
Mormonism - Latter-day Saints
Jehovah's Witnesses
Christian Science
Armstrongism
Christadelphians
Oneness Pentecostals
Unification Church
Unity School of Christianity
Scientology - Dianetics