Phasma's blaster rifle
Captain Phasma utilized a unique F-11D blaster rifle manufactured by Sonn-Blas. This blaster served as her personal weapon and was equipped with a buttstock, a chromium coating, and a specially designed recurved trigger guard allowing for a two-handed grip.
Description

While serving the First Order, Captain Phasma wielded her custom blaster rifle. The rifle was covered in recovered chromium, matching the distinct armor worn by its owner. Unlike standard F-11D blasters, Phasma's version did not have a complete trigger guard. The weapon's barrel also incorporated heat dispersal vents, and its extended stock contained a reservoir for gas.
History
Phasma secretly commissioned the blaster a year after she joined the First Order. By the time she went back to her homeworld, Parnassos, to assemble her armor, the blaster was already calibrated to her gloves.

In 34 ABY, Phasma brought her blaster to Jakku and, under the orders of Kylo Ren, used it to execute surviving villagers after the stormtroopers attacked following the death of Lor San Tekka. She also had the weapon with her when she was thrown into the trash compactor on Starkiller Base. After escaping, she tried to eliminate Lieutenant Sol Rivas with the rifle, but failed as the base was being destroyed.
Later that year, Phasma had her blaster on the Supremacy, the flagship of Supreme Leader Snoke. She was preparing to oversee the execution of Finn for his treason against the First Order, but the Supremacy was split apart when the Raddus, General Leia Organa's flagship commanded by Vice Admiral Amilyn Holdo, crashed into it. Finn then used an executioner trooper's BL-155 Laser ax to destroy Phasma's blaster, leading her to use her baton in combat.
Behind the scenes
Originally, Phasma's blaster rifle was conceived as a heavy weapon for stormtroopers in Star Wars: Episode VII The Force Awakens. It was redesigned for Star Wars: Episode VIII The Last Jedi with a slight color adjustment to better match the chrome of Phasma's armor. Matthew Savage noted that the blaster in The Force Awakens had a more gold tint compared to the one in The Last Jedi, but he was unsure if Rian Johnson specifically requested a more chrome appearance.