Redshift, Rocketeer Chief

Legendary Creature — Goblin Pilot

Vigilance

: Add X mana of any one color, where X is Redshift's power. Spend this mana only to activate abilities.

Exhaust — : Put any number of permanent cards from your hand onto the battlefield. (Activate each exhaust ability only once.)

Exhaust abilities can be activated any time you could normally activate an ability.
If an exhaust ability of a permanent is activated, and then that permanent leaves the battlefield and returns to the battlefield, it becomes a new object so its exhaust ability can be activated again.
If an ability triggers whenever you activate an exhaust ability, that ability resolves before the exhaust ability resolves.