An explosive firework. Was sold in the United States until the Child Protection Act banned them in 1966 because of the large amount of injuries due to mishandling or stupidity. An M-80 is usually about 1-1/2" x 9/16" with the inside of the tube filled with flash powder. One M-80 can easily remove fingers or send particles into the eyes causing permanent blindness.
"Dude, did you see that M-80 go off? It blew apart that entire mailbox!"
"I know I don't have a hand anymore, I lit an M-80 in my hand and it just blew it clean off. I would give you the finger but I have none left."