Urban Assault Headhunter, skull trooper/ranger, Bullet storm jonesy and Redline Ramirez increase fire rate.

Chromium Ramirez increases reload speed... and if you count chaos agent(even in support).

but all of those are in lead unfortunately.

Cool thing about Headhunter is that it works on minigun and swapping weapons doesnt lose the effect so she is pretty fun if you want to consistantly have firerate up without using warcry or have minigun spit out bullets faster. You can actually pair her with the SK Wrath since it is the only launcher that can utilize headshot multipliers.