Blasting Station + Trapjaw Kelpie + Hardened Academic

Blasting Station

Trapjaw Kelpie

Hardened Academic

How it works

1. Activate Blasting Station by tapping it and sacrificing Trapjaw Kelpie.
2. When Trapjaw Kelpie dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Hardened Academic and Blasting Station trigger.
4. Resolve the Hardened Academic trigger, putting a +1/+1 counter on Trapjaw Kelpie.
5. Resolve the Blasting Station trigger, untapping it.
6. Resolve the Blasting Station ability from step 1.
7. Repeat.