A small high powered energy gun which fires orange lasers, or more specifically, positron collider blasts. It is the primary side-arm of the Middleman. It can disintegrate demons made of earth and, as seen in "The Palindrome Reversal Palindrome", can penetrate body armor and kill a human being with a single shot.
There are at least two major variations. The Middleman carries a longer-barreled version, which operates in two stages. A single pull of the trigger activates the weapon, extending the barrel and raising a sight on the top of the gun. Different pulls of the trigger either fire the gun or return it to its inactive stage.
The second version is wielded by Wendy Watson, and is a much shorter, boxier version. This variation can be turned off by remote to stop someone, especially a trigger happy Middleman-in-training, from firing it. It is unknown whether the Middleman's Middle-Gun has a similar safety measure, but it is likely that it does not.
As seen in "The Obsolescent Cryogenic Meltdown", the 1969 Middleman, Guy Goddard, preferred a silenced gunpowder firearm, rather than a positron-collider weapon.
Though the Middle-Gun is extremely powerful, it also has weaknesses. Some metals (notably that of The Candle's melting ray) are strong enough to reflect its blasts, and some types of radiation (such as those emitted by Eleanor Draper's Quantum Processor) can negate its effects.