Loot, the Pathfinder

Double strike, vigilance, haste
Exhaust — {G}, {T}: Add three mana of any one color. (Activate each exhaust ability only once.)
Exhaust — {U}, {T}: Draw three cards.
Exhaust — {R}, {T}: Loot deals 3 damage to any target.

Muraganda Raceway

Start your engines! (If you have no speed, it starts at 1. It increases once on each of your turns when an opponent loses life. Max speed is 4.)
{T}: Add {C}.
Max speed — {T}: Add {C}{C}.

Rangers' Aetherhive

Vigilance
Whenever you activate an exhaust ability, create a 1/1 colorless Thopter artifact creature token with flying.
Crew 1 (Tap any number of creatures you control with total power 1 or more: This Vehicle becomes an artifact creature until end of turn.)

Elvish Refueler

During your turn, as long as you haven't activated an exhaust ability this turn, you may activate exhaust abilities as though they haven't been activated.
Exhaust — {1}{G}: Put a +1/+1 counter on this creature. (Activate each exhaust ability only once.)

Amonkhet Raceway

Start your engines! (If you have no speed, it starts at 1. It increases once on each of your turns when an opponent loses life. Max speed is 4.)
{T}: Add {C}.
Max speed — {T}: Target creature gains haste until end of turn.