Book of Virtues: A stationary wisp spawns where Isaac was when he threw his head that fires tears in the same direction Isaac does. The wisps do not persist between rooms.
Found Soul: Will throw a Found Soul head. This head will not be returned upon recalling Isaac's head. Each use creates a new throwable head which makes Isaac capable of creating a minefield of Found Soul heads which all deal contact damage. All heads disappear upon holding the item, but reappear once the head is thrown. Only the most recently thrown head will fire tears.
The Forgotten: The head changes in sync when switching between The Forgotten and The Soul. The Forgotten's bone attack still belongs to the body, while The Soul's tear attack belongs to the head as expected.
Tainted Forgotten: Throws the head of Tainted Forgotten, but the bone attack still remains on his body. Tainted Soul can't help to retake his head. Due to lack of movement, the head can only be recalled by reactivating the item, or by throwing the body towards with Tainted Soul.
Incubus/ Tainted Lilith: The tear from the Incubus fires from near the head, but Incubus still visually follows / comes from the body.
Recalling the head while it's still in the air will cause the head to quickly zip above Isaac's body, and it will stay like that even after using the item again. This makes Isaac very difficult to hit, offering great protection against all forms of damage.