M36 Revolver
It might not do the most damage, but it’s light, easy to reload, and it’s the most common. You can find it and its ammo everywhere, which is a big plus.
Light and easy to carry. I can run for miles with it on my back.
Reloaded it in seconds, no pain, no stress.
Found it in a cabinet, and the ammo was right there with it. Easy.