Musaylimah Ibn Habib (aka al-Kadhdhab, 'the Liar'), but did you ever wonder what he taught that was different from Muhammad?
(Miscellaneous)
This is what I got from Wikipedia. The source given is the seventh chapter of the Dabestan-e-Mazaheb, a 17th century comparisons between religions and sects. His religion is referred to as 'Sadakiah' in the text.

If you google the Dabestan-e-Mazaheb, you can find some translated PDF copies of it. I wanted to download one and check it out and possibly link it here so that whatever the Wikipedia page says can be verified, but for some reason am not being able to download it. If anyone has some other sources, I'd definitely like to see them.

Anyway, here's what he said -

Musaylimah taught 3 daily prayers to God, facing any direction. He criticized Muslims for selecting Kaaba as the direction of prayers, saying that God is not limited to one direction. Musaylimah declared that the Kaaba was not the House of God, because an all-powerful God has no house. Musaylimah said fasting should be at night instead of daytime during Ramadan. He prohibited circumcision. Musaylimah considered men and women equal, and allowed premarital sex. Musaylimah prohibited polygamy and cousin marriage. Musaylimah declared that any slave who converted to his religion would become free. Musaylimah stated that Iblis did not exist, because a fair and merciful God would not allow a being like Iblis to throw people into error. Musaylimah also said it was wrong to include his name or any prophet’s name in worship to God.

I don't believe in stuff like prophets and revelations, but IMO Musaylimah sounds like a far better guy than Momo. No wonder Muslims always portray him in a negative light. Gender equality?! Premarital sex allowed?! No polygamy?! No slavery?! HARAM!!!!! (Lol).

Edit - Apparently he also made up his own book, called the Furqan. One of its verses is supposedly very similar to the Quran's 100th verse. Quran challenge met? Hmmmm.....