In a 2v2 game, can Tide Turner be used to swap a teammate's unit onto your controlled battlefield during combat?

Ruling: No, Tide Turner cannot be used on a teammate's unit. The card's errata explicitly specifies it can only target "your unit," not an ally's unit.

Nuances:

• An ally's units can never enter a battlefield controlled by you
• Combat can never happen with more than 2 units from different players involved at the same battlefield