I have compiled a list of the best Colonial Marine Weapons
Do you agree and what else would you have ranked in the list?

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Would the weapon have to have been in either a game or in the movie?

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I have included weapons from both movies and games. Hard to get 10 weapons out of Aliens

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What if you expand the selection to cover all of the films?
Alien gives you the laser pistol (unused), flame unit and harpoon gun.
Aliens give you VP70, S&W pistol, M41A pulse rifle, M56 smart gun, M240 flame unit, shotgun, sentry gun, grenades
Nothing new in Alien 3
Alien Resurrection gives you collapsible shotgun, zip gun, wrist gun, collapsible grenade launcher (all used by the crew of the Betty), USM pistol, double burner, shockrifle, grenade

That gives you 19 from the first four films and 11 just from the first two.

Prometheus adds another flamethrower and a pistol and Covenant adds rifles based on the AR15/M16 and Steyr AUG as well as another shotgun at least.
I've not included the Alien vs Predator films but those would add lots more contemporay weapons as well as those used by the predators.

I was going to say the P.I.G. (Phased Plasma Infantry Gun) from the tech manual.

_________________
"Awww, someone tell me that's a boot!

It's a boot!"

III drops