A common tendency in from the 19th century on has been religious universalism. Several major prophets have appeared to spread this message.
Perhaps the best known is Baha'ullah, the founder of the Baha'i faith. He claimed to represent a new cycle of prophecy, and to found a universal non-sectarian religion for this age (19th/20th century on). In a sense he tried to unify the various world religions, especially the monotehistic religions . In practice he failed dismally (well in this writers humble opinion). Notwithstanding the great saintliness of Baha'ullah himself, anyone who encounters Baha'is finds a sort of liberal/reform Islam there - sort of an Islamism that is acceptable to the Western (Judeo-Christian) mentality. Their teachings have much of moral worth, but metaphysically and theologically I find them disappointing. (Although perhaps this is just my own lack of insight and knowledge into what they are saying).
More recently, the Hindu holy man Shri Sathya Sai Baba claims to be a new avatar who has come to reveal the truth of all religions. He says to his followers - don't worship me, follow the religion you were born into. His crest includes symbols for the following five religions: Hinduism, Buddhism, Zoroastrianism, Islam and Christianity. Again, his teachings are of great moral worth but there is nothing original in them (they are a sort of syncrestic popular Hinduism - elements of Gita, Advaita Vedanta, etc).