Fire-breath

Fire-breath is an ability that several Transformers with reptilian beast modes have installed in themselves for combat in their alt modes.

The Transformers cartoon
The Dinobots had fire-breath included in their alternate modes. Although they all possessed the ability, Grimlock and Slag were the only ones that really employed it. Slag used his fire-breath to help repair the Washington Monument, and Wheeljack had Grimlock demonstrate his mastery of his fire-breath by adjusting Blaster's volume levels. Later, while practicing on Dinobot Island, Grimlock had Slag practice his "fire stuff" (Grimlock's words) by evaporating a pond. Slag displayed good moves. The local wildlife was not amused. Later, Slag's fire-breath saved the Dinobots by evaporating the tar pit they had sunken into, but it made him rather tired.

The Headmasters cartoon
The Monsterbots also have fire-breath.

Toy bios
As a point of fact, Slag's very function is "flamethrower".

Commercial appearances
Trypticon once attacked the Protectobots with a blast of fire-breath.