I think they should make a special spree for every type of weapon or weapon class (if they are included in reach if not they should be available in forge or from the player weapons menu at least)for example
Spartan laser: Laser Spree (5 kills), Glowing red(10 kills)
Rocket launcher, Fuel rod, Missile pod, frag grenade, trip mine, brute shot Etc: explosive Spree(5 kills) Explosion man(10 kills)
Plasma Rifle, Plasma pistol, Plasma cannon Brute, plasma Rifle, Etc: Plasma Spree(5 kills) Plasma Burner(10 kills)
Flamethrower, Flame Grenades Etc: Flamer spree(5 kills) Pyromaniac(10 kills)
Needler : Needler Spree(5 kill) Pink Death(10 kill)
AR, SMG(reg & silenced), Machine Gun turret, spiker ETC: bullet spree(5 kills) Spray & kill(10 kills)
BR, carbine, Magnum, ETC: head spree(5 kills), Marksman(10 kills)
assassinations: assassin spree(5 kills) Hit man(10 kills)
these would be the spree metals I'd add on top of the vehicular, sniper, sticky Shotgun(I'd add the mauler to this)
Hammer, & sword spree series.