So one of my first times pldnd I was a dual welding fighter with one long sword and one small mace. My friend was a druid with a hawk companion. Well we had to get into a mausoleum to break a artifact that was creating undead. We soon get out numbered and thankfully we both had blunt weapons (he was using a quarterstaff) when it came to his hawks turn we rolled for it to come down and scratch at the zombies we couldn't reach. Nat 20 so dm made the bird MISSILE RIGHT THRU ZOMBIES HEAD KILLING IT INSTANTLY. druid then buffs the bird up with the last of his spells making it a beast.
The bird starts killing more undead then me the fighter until a zombie grab the bird in a grapple. In my valiant efforts to save our greatest killer I throw my mace at the zombie. Nat 1 rolled.
The dm tells me to roll dmg and I roll the full d6 and KILL THE BIRD INSTEAD. my druid friend then gets upset and continues to fight until we die cause of bad rolls and damage.
Moral of the story? Don't try to save a friend by pretending your thor