OK, worst roll... not ever, but recently.
Last night, we were fighting undead. The fire-themed wizard says, "Undead burn nicely."
Then his first fireball (9d6) does 15 points of damage (4, 2, 2, 1, 1, 1, 1, 1, 1, 1). That's an average roll of 1.67. You can imagine the looks we gave him...