M249 has 100 shot but a damage from 14!
That means you need more then 1 shot.
Grenade Launcher doesn't kill with 1 shot (If enemy has full energy) .
Rocket Launcher doesn't kill with 1 shot too!
And the RPG Launcher is bad because after every shot you have to reload and in this time you often die.
Laser has a fast reload time and has 15 shot.
And if enemy has armor and you miss the shot with RPG launcher you will hit the enemy but he dont die.
And with laser you can shot faster then the RPG Launcher.
And the best:
You can change the colors of laser
Each of those weapons is good, but it needs to be used wisely I mean, Grenade Launcher can easilly kill enemies behind corners, it's great against buildings whose are hidden, etc. Rocket is quite same as Grenade Launcher, but the missiles are fast and can't bounce like grenades do. RPG - great against players, i mean:
Can easilly destroy buildings (Turrets, Teleports, Dispensers/Supplies), but it's flight time is slower than Rocket Launcher (or quite same).
Laser is strongest single-player-nuke, or single building nuke, kills everything with one shot (only Super Armor absorbs 1 shot, second is deadly), and destroys Wall III with 2 shots also.
Hmmm, that's practically all, no one of these weapons is the best