Get plenty of these:
How about a little reality in this discussion.
If a species capable of extra celestial travel were to choose to invade earth I doubt that we would ever get the opportunity to use weapons of any kind in defense.
Such a species if they desired to take Earth for their own could most likely engineer a human specific virus to wipe out the human population.
If for some reason they decided that humans would make a good slave population (I can’t think of a reason that a so advanced civilization would need slaves) they could engineer a virus to lobotomize we humans making us passive.
It is most likely that the war would be over before we knew we were under attack. We would for all intents and purposes be at their mercy.
My 12 ga remington 870 marine magnum, with a case or two of rifled slugs would seem to be the way to go.
If it will kill a bear, it should kill an extraterrestrial.