If I Temporal Breach a unit that's equipped, what happens?

The equipment detaches and the unit comes back unequipped.

When Temporal Breach banishes the equipped unit, the unit moves from a board zone to a non-board zone (Banishment), which breaks the attachment — the gear detaches and stays at the unit's last location (Rule 435.4.b). The unit is then played back to that same location, ignoring its cost, as a fresh game object: no equipment, no buffs, no damage (FAQ #11709). If the unit was at a Battlefield when banished, the now-unattached gear will be Recalled to its controller's Base at the next Cleanup (Rules 435.4.a, 457.1). One caveat: if the unit was a token, it ceases to exist in Banishment and never returns (FAQ #11668).