Note: This research was done by PlatinumPlayer3 on the Twisted Metal subreddit. Everything here is his research, which I trust is accurate.
I did my own research into special weapon damage for the heck of it.
Note: All DMG is approximate.
In order of most damaging to least damaging:
Minion (Flamethrower): 120
Minion (Fireballs): 75
Crazy 8 (Maximum Charged DMG): 75
Outlaw (With All 10 Missiles): 55
Crazy 8 (Maximum Non-Charged DMG): 50
Darkside (T-Slide Bonus & Wall Ram Bonus): 50
WartHog: 50
Shadow (Turret): 46
ManSlaughter: 43
Sweet Tooth: 43
Outlaw: 43
Mr. Grimm: 43
Axel (Spike Tires): 40
Darkside (T-Slide Bonus): 40
Roadkill (Charged): 40
Crazy 8 (Realistic Charged Damage Output): 38
Darkside (Wall Ram Bonus): 35
Roadkill: 35
Crazy 8 (Realistic Non-Charged Damage Output): 34
Spectre: 30
Yellow Jacket (Turbo Ram): 28
Shadow: 25
Junkyard Dog: 25
Darkside: 25
Brimstone: 23
Yellow Jacket (Non-Turbo Ram): 20
Axel: 13
Yellow Jacket (Spike Projectile): 9
My thoughts:
-Brimstone's special is cool but it simply sucks. That car as a whole sucks.
-If Axel didn't have that alt special he'd be awful.
-Shadow's Turret is a much more useful special, just like Axel's alt.
-Spectre's special is ranked the worst by the stat screen (5/10) when YJ, JYD, and Brimstone all don't have a more damaging special yet they're all 6/10..