1) Strict Unitarians believe in God the Father as God, that Christ wasa good man and teacher--but not God. And that the Holy Spirit is God's presence in the hearts of men.
2) Modalism (Monarchianism) is the belief, held largely by Oneness Pentecostals, that the Father, Son, and Holy Spirit are three modes of existence for the One God--- Father, Son, and Spirit are only different names for the same Person.