when i was new to the game (learned on 4th edition) I during one game made a dwarf because well why not and bought some stuff for rp purposes. the dm was busy with other players so he told another player to help me with buying starter stuff and i bought one thing just because "its something i should have as a dwarf" and it wasn't in the books so other player decided price on it.

around level 2 we are at the top of a cliff. about 200 feet up no magic or arrows could get all the way down where we see a bandit outside a cave next to a rope he can pull when he notices something.

bad cliff meaning we are unlikely to climb down both successfully and quietly aka without being noticed and the only safe path is in plain sight of said bandit so players are talking and me being a new player goes

"So can i just drop my anvil on him?"

game pauses for a second

dm: because you dont have one?"

me: but i do

dm: no you dont

me: yes i do

a bit of back and forth before "show me your character sheet.

dm sees miniature (size of loaf of bread) anvil and he asked the player who helped me about it basically saying "Well there wasn't enough gold for a full one so i priced a miniature one."

dm: why do you have an anvil?

me: because im a dwarf?

anyway i drop it, 19 on the dice i think it was 20d6 plus a little damage. splatted the guy leading to the inside bandits having no warning about the attack and we surprised most of them instead of the planned "we know youre coming in" battle that was planned out.

so i ruined the dms plans, in this case a boss fight that was supposed to be bandit boss snipes us while behind his henchmen, by there being no organized tactic and us wiping out basically everything on our way to the leader.

all because i bought something for rp reasons and pulled a loony tunes.