Overall, outside of Islamic (or Shi'ite) Orthodoxy, my continually biggest fascinations and obsessions are obviously:
John Dee/Edward Kelly/Enochian Magic
Sabbatai Zevi/Jacob Frank/The Donme
The Bab/Babism
Aleister Crowley/Thelema
This is leaving aside Dharmic stuff.
The four subjects above all seem to intersect in many ways. To a lesser extent I would also connect Jesus, Paul of Tarsus and the Apocalypse of John to this overarching interest, however even though there are antinomian tendencies in the ways Jesus and Paul are interpreted by Christians, it still leans far too much over to moralism (in what is contained in the New Testament) than having a strong enough root in the above four.
The Apocalypse of John does obviously relate to John Dee and Aleister Crowley.
The Bab on the other hand claimed to be the Imam Mahdi, much like Sabbatai Zevi claimed to be the Jewish Messiah.
There are interesting parallels between Jesus, Zevi and the Bab.
Anyway all of these intersect with their hyper-esoteric, occult, mystical, magical and antinomian aspects combined with very obvious apocalyptic undertones through all of these figures. At the same time, they are all subject in the mainstream to conspiracy theories about them, often utterly absurd.
They're all some of my favorite people to study with their own strange histories and very enlightening metaphysical insights - again leaving aside Shia Islam which is my orthodoxy with the Qur'an, Muhammad and Twelve Imams.
One thing also about the above (including Jesus himself too) is that the concept of Messianism itself seems to be very strongly esoterically tied to heresy itself.
On the eXoteric level, having studied (and continuing to) all of these figures, here is an overview of how these 'heresies' intersect:
1. Jesus (the most famous and popular Jewish Messiah Claimant), according to Christians, claimed to be God-incarnate, a heresy against Jews. Also never fulfilled any of the expectations that Jews expected of the Messiah, so was a heretic in his claims on that basis as well.
2. Jesus according to Paul, abrogated the Torah, a heresy against both Jesus and Jews
3. Muhammad received revelation (Qur'an) which affirmed Jesus as Messiah but staunchly denied Jesus ever claiming to be God-incarnate - a 'heresy' to Christians, and a re-establishment of Jesus as a Jew.
4. Dee and Kelly in their Angelic transmissions, received some confirmation that Jesus was not God-incarnate but also denied other Abrahamic theological doctrines, a heresy against Christianity (and against Dee's own beliefs) and a confirmation of aspects of Islam without ever mentioning it
5. Sabbatai Zevi, claimed to be the Jewish Messiah, encouraged transgressing the Torah (law) to liberate the world from it's current fallen state, a heresy against Judaism. Not only that Zevi ended up converting to Islam in 1666, while inwardly still being a Kabbalistic Jew
6. The Bab claimed to be the Mahdi, claiming his own new scriptures and tradition and new prophetic cycle, a Heresy against the finality of Muhammad in Islam and against the traditional orthodox Shi'i view of the Mahdi
7. Crowley both affirmed and denied conceptual tendencies (typified by the Antinomian) in all of the above, but did not make claim to the Abrahamic tradition, nor the Dharmic tradition, rather claimed their major figures where part of rather the Thelemic current*
(*as found best outlined in the Book of Lies, Chapter 7)
That outline is only the surface level as it goes way further than just that.
Also with Zevi/Frank like with The Bab and his followers, the later idea of immersing in other traditions with your true beliefs concealed, or actively practicing another religion and taking on it's belief system, became a shared trait with Crowley, Chaos Magic, the O9A later on.
Though this, due to persecution and not malicious intent, kind of goes back to Shia Islam (through the concept of Taqiyya - which conspiracy theorists love and which is utter bullshit, a total intentional misrepresentation of a concept) and not Judaism/Zevi/Frank per se, though not so much in the context of pretending to follow another tradition. For Taqiyya, one would still say they are a Muslim (and it's in the context of Sunnis persecuting Shia) but one would not explicate the details of their beliefs as a Shia and would tend more towards generalities shared with Sunnis in order to not be singled out.
Though of course Jews had to put up with lot of persecution at various times, typified by the Babylonian Exile, but such a concept didn't seem to exist back then.
