Fire Bar

Firebars are rotating rods made of fireballs generally found in fortresses. They debuted in Super Mario Bros.. Although not a living enemy, they go swinging around trying to hurt Mario or Luigi. In later games, they were replaced with similar-acting enemies such as Roto-Discs and Ball 'n' Chains.

In Paper Mario, the Firebars reappeared in Koopa Bros. Fortress and Mt. Lavalava; this time they swing sideways. They also swing either clockwise or counter-clockwise, if Mario touches one; he loses some HP. Jumping over one of these Firebars causes it to swing faster. If Mario dodges one 10 times, it will vanish and drop a number of coins. This is the only appearance that Firebars can be defeated.

Firebars were the only enemies of the original Super Mario Bros. to not be featured again in Super Mario Bros. 3. They also appear in later Mario games, including Super Mario Bros.: The Lost Levels, Super Mario 64, New Super Mario Bros., Paper Mario: The Thousand-Year Door, Yoshi's Island DS, Mario vs. Donkey Kong 2: March of the Minis, Super Paper Mario, Super Mario Galaxy, New Super Mario Bros. Wii and Super Mario Galaxy 2. Firebars also made appearances as obstacles in the later Mario Kart games. Firebars were also given notable appearances in certain castles of Super Mario World 2: Yoshi's Island, which depicted them as swinging three-dimensionally. A three-dimensional Firebar depicted with eyes also appeared in the Bowser's Castle course of Mario Kart: Double Dash!!.

Super Paper Mario Tattle
"That's a Fire Bar. Don't touch it, or you'll get burned..."

Trivia

 * Firebars were featured as collectible items in Animal Crossing: Wild World and Animal Crossing: City Folk. When it is set down, it plays the castle music of Super Mario Bros. while the Firebar spins.
 * In The Legend Of Zelda: A Link to the Past, Firebars spin on the ground.
 * According to Satoru Iwata, "...firebars, which appear in Super Mario Bros., had also been used early on in development of The Legend of Zelda: A Link to the Past."