Frontier Justice

Overview

Frontier Justice is the unlock weapon associated with first Engineer Milestone (unlock 5 Engineer achievements).  Frontier Justice only holds three shotgun rounds with a maximum of 32.  The gun has no alt-fire functionality and operates like the regular shotgun.  The weapon is very tied to the performance of the Engineer's sentry gun, specifically the amount of kills the sentry has amassed.  Upon destruction of the engineer's sentry (either by enemy or demolition), the number of kills the sentry currently had is transferred into critical shots to be fired by the Frontier Justice.   The gun has a new kill icon distinct from the regular shotgun.

Critical Information

When his sentry is destroyed the sentry's kill amount is converted into critical shots, gaining two shots for every sentry kill.  The Engineer automatically uses the criticals upon firing and may amass up to 35 critical shots to be used at the player's discretion.  The amount of stored critical shots are displayed in a counter on the bottom right hand side of the screen above the ammo information on the UI.  The gun also glows to show off its critical abilities such as after winning a round or from the Medic's Kritzkrieg ubercharge.

History

The Frontier Justice was presumably designed by Radigan Conagher (The Engineer's Grandfather).  A cache of Radigan's blueprints were recently uncovered by Blutarch Mann and given to the Engineer in the hopes of fixing Radigan's previous inventions.  Amongst the blueprints was folder with the label of GUNS and locations of Australium caches.  It is likely that with his grandfather's deciphered blueprints and Australium the Engineer was able to create the Frontier Justice as well as other devices seen in the Engineer update. 

Guitar Taunt

The Frontier Justice comes with a brand new taunt utilizing an acoustic guitar seen during the Meet The Engineer video.  The Engineer pulls out his guitar from behind his back and briefly tunes/strums the instrument before attacking with an overhead smash.  The attack causes the guitar to break into several pieces, which can be seen on the battlefield but not picked up.  Continuing in the line of TF2 Taunt Attacks, the guitar may be used to kill enemy players if they are struck by the guitar swing at the end of the taunt.  The guitar also has its own unique kill icon seen by players when someone is dispatched via guitar.