In the Outer space battles, the weapon you're carrying is your life warranty, better weapon is a synonym of more chances of surviving.
Here you can see the most useful weapons in the galactic wars:
1. Outspace gunslinger with two Handguns and Artic gunslinger with the same.
2. Earthling carrying a Plasma Beam
3. The most common rifle in space, with bayonet in the end
4. Newest model of Assault Rifle (idea taken from John Moffat)
5. Assault Rifle with bayonet (you can see the bayonet is applicable on many weapons)
6. Heat-guided misile launchers
7. Overused .30cal Chain guns