Fire-retardant foam

Fire-retardant foam is a foam used to retard fires. It is also among the mightiest weapons known to Transformerkind. Even across the generations, the legendary power of fire-retardant foam may be slightly diminished, but it is still to be feared and respected.

It is sometimes dispensed from fire extinguishers.

The Transformers cartoon
When the Autobots were disabled by a Decepticon sneak attack, Spike prompted the Autobot computer Teletraan I to release fire-retardant foam. The foam landed on the Decepticons and immediately shorted out their circuitry. Recognizing this unbeatable foe, Megatron ordered an immediate retreat.

The Autobot Ironhide was also capable of releasing the substance, among other compounds, from a nozzle embedded in his wrist. That guy could shoot just about anything. Why he never used its almighty power to annihilate the Decepticons once and for all is not known.