Weapons Damage Rate of Fire Ammo Capacity Magazine Size
Assault Rifle High High High High
Handgun super Medium Medium Medium
Shotguns High Slow - Medium Medium Medium
Sniper Rifle High Low Medium Small
Rocket Launcher High Low Low Small
Grenade Launcher unmilted Medium Low Small
Plasma RIfle Decent High High High
Alien Lightning Gun High High High High
Railgun High Medium Low Small
Mines High Medium Low N/A
Turret Placer High Low Low Small
Grenades High Low Low N/A
Flash Grenades None Low Low Low
Melee Disc High Low Infinite N/A

Quick Summary of Weapons:

Dual Handguns: A medium damaging weapon, they should be used for most story mode missions, also good in multiplayer but not your first choice.

Assault Rifle: A close to long range weapon, is good for all story missions, should be used for close range in multiplayer.

Pump Action Shotgun: A close range weapon, is good for most story mode missions, should be used in multiplayer for close range.

Auto-Shotgun: Same as the Pump action, but you don't need to reload after every shot.

Sniper Rifle: A long range and deadly weapon, should not be used in story mode, but is a deadly weapon of someone skilled in accuracy. This is my favorite weapon in multiplayer.

Rocket Launcher: A long range weapon, should be used to take down mechs in story mode, a good explosive weapon for multiplayer.

Flamethrowers are short range.