Nunu & Willump vs Rammus

Cast Biggest Snowball Ever! (W) from far away for your ganks: the longer it rolls, the bigger it gets, and the more its damage and knock-up grow.

Hit your target with all three snowballs of Snowball Barrage (E): they're slowed, then at the end of the spell, Willump roots nearby slowed enemies.

Cast Absolute Zero (R) on enemies who are already immobilized: the slow grows stronger, and the explosion hurts more the longer you channel.

Save Consume (Q) to finish the dragon or Baron with Smite: against a monster, the bite deals true damage and heals you.

Stay behind your minions: Powerball (Q) stops on the first enemy it collides with, minions included.

If you deal magic damage, lean on it in trades when Defensive Ball Curl (W) is on cooldown: without it, his resistances drop to those of an ordinary tank.

If you're ranged, don't let him reach melee range when Frenzying Taunt (E) is ready: its range is short, and it forces you to attack him.

Get out of the Soaring Slam (R) area fast: aftershocks repeat the slow there, and if cast during Powerball (Q), it adds a knock-up in the center.

Don't attack during Defensive Ball Curl (W): each auto returns magic damage to you, and he gains armor and magic resist.