Splinter Twin + Nurturing Presence + Barrenton Medic

Splinter Twin

Nurturing Presence

Barrenton Medic

How it works

1. Activate Barrenton Medic by tapping it, creating a token copy of itself with haste.
2. When the Barrenton Medic token enters the battlefield, the nontoken Barrenton Medic triggers, giving itself +1/+1 until end of turn.
3. Activate Barrenton Medic by putting a -1/-1 counter on it, untapping it.
4. Repeat.