Oil Drum

From the Super Mario Wiki

Oil Drums are gray, as the name would imply oil drums.

Oil Drums first appeared in the Donkey Kong arcade game. Here they are found in several levels and are quite harmless, unless a barrel ends up being burned up inside them, then they will produce Fire which can harm Mario.

Oil Drums later appear in Donkey Kong Country. In this game Oil Drums have two attack patterns, they either expel flames which can injure Donkey or Diddy or they will expel enemies (most commonly Slippas). In the level "Oil Drum Alley" Donkey and Diddy must jump from one floating Oil Drum to the next (while they are not spurting fire of course) in order to reach the levels end. Oil Drums can only be destroyed by throwing a TNT Barrel at them. Donkey Kong Country game also has an Oil Drum boss named Dumb Drum.

Oil Drums also appear in the semi-sequel to Donkey Kong Country, Donkey Kong Land. There is no real difference between the Oil Drums of Donkey Kong Country and the ones of Donkey Kong Land.

In Donkey Kong Country 2: Diddy's Kong Quest and Donkey Kong Land 2 a tipped over Oil Drum can be seen in the background of Klubba's Kiosk.

In DK: Jungle Climber, there are barrels the resemble Oil Drums called Oil Barrels.