Another subject that has come up is Pentecostal Oneness, a different form of Unitarianism. (I don't know if they consider themselves Unitarians, but they believe Jesus is the Father, the Son and the Holy Spirit.)
Modalistic Monarchianism, also known as
Modalism or
Oneness Christology, is a
Christian theology upholding the oneness of
God as well as the
divinity of
Jesus; as a form of
Monarchianism, it stands in contrast with
Trinitarianism. Modalistic Monarchianism considers God to be one while working through or existing as the different "modes" or "manifestations" of
God the Father,
God the Son, and
God the Holy Spirit, without limiting his modes or manifestations.
[1][2]
In this view, all the
godhead is understood to have dwelt in Jesus from the
incarnation, who they understand to be a manifestation of
Yahweh in the Old Testament. The terms "Father" and "Son" are then used to describe the distinction between the
transcendence of God and the incarnation (God in
immanence).
[3] Lastly, since God is a
spirit, it is held that the Holy Spirit should not be understood as a separate entity but rather to describe God in action.
Modalistic Monarchianism is closely related to
Sabellianism and
Patripassianism, two ancient theologies condemned as heresy in the
Great Church and successive
state church of the Roman Empire.
[4][5]
Modalistic Monarchianism - Wikipedia