Umbra

Umbra is a Decepticon character in the Generation 1 continuity.

Here comes a chopper to chop off your head!

Umbra was a Decepticon assassin who attempted to murder Optimus Prime during the early stages of the Great War. He was fanatically devoted to the Decepticon cause, and was fully willing to die to further their agenda. He transformed into a pistol small enough to be held by his fellow Decepticons.

(Note: Umbra is never referred to by name in the comic itself. His name was given by author Simon Furman in later interviews.)

Fiction

Dreamwave Generation 1 Comics

I wish I knew how to quit you, Darklight.

Along with Backbite and Darklight, Umbra invaded the Chamber of the Ancients in Iacon, just as Optronix accepted the Matrix of Leadership and became Optimus Prime. After killing a guard and literally disarming Skids, Umbra transformed into his energy rifle mode and lent himself to Darklight. Knocked away by Prime, he transformed back to robot mode and attacked the Autobot leader again and accidentally slew Darklight. With both of his comrades dead, Umbra was briefly interrogated by Prime. He cryptically warned the massed Autobots of 'impending doom from below' before messily committing suicide with acid.

This is what happens when you drink Windex and Pop Rocks at the same time

(Note: When Optimus Prime knocks Umbra into the wall, Japanese characters can be seen on his leg. This is actually the logo for Microman, a Japanese toyline from which many early Generation One toys, such as Soundwave and Megatron, were taken.)

From Teletraan I: The Transformers Wiki, a Wikia wiki.