Junkyard Dog MK III is Sol Badguy's main weapon in Guilty Gear Vastedge XT and Guilty Gear Xrd -SIGN-. The sword has a rectangle-shaped blade, and a red and white color scheme. It also has a secondary function as a long-range weapon that can fire a high-level energy spell called Saint Oratorio.
Junkyard Dog is a combination of Fireseal and the Flashing Tooth, which further amplifies Sol's fire magic. Sol has also modified Junkyard Dog MK III to reconfigure into a long-range cannon that can fire intense magical burst of energy, this spell being known as Saint Oratorio, which is a powerful Magic Art specifically created to work in concert with the OutRage. 
- As a coincidence, in the older Guilty Gear games, the Fireseal's appearance resembles a gas lighter (much less so in Guilty Gear 2: Overture), while the Junkyard Dog looks like a Zippo lighter. When the casing of Junkyard Dog is unlocked, it resembles a dragon's maw (likely an intentional reference to Sol's Gear form).