It was the second or third game I ever played, multiplayer, and we were doing a frontal assault on the goblin camp, over the main bridge. Someone fired an acid arrow, at a cluster of 3 goblins, and it splashed, leaving a small puddle of acid on the ground. Another player threw a satchel charge, thinking it was a grenade, and it just landed on the ground -- right in the acid puddle -- and sat there. Realizing their mistake, they figured they could just pick it back up or set it off in a subsequent round. Our rounds ended, and the game went on.
For the environmental movement at the end of that turn, the acid ate through the sack, spilling the explosive powder in a fairly wide area all over the bridge. I suddenly noticed all the other barrels of powder and firewine on the bridge itself. I jumped in and asked the character whose turn it was to just cast a flame dart cantrip on the powder -- not the enemies.
The whole dang bridge went up, killing around seven enemies. The explosions just kept going.
A botched throw, lack of understanding of the tools at hand, a random puddle of acid, some really detailed environmental coding, and we wind up with an opportunity nuke.
