There's two very effective melee items when it comes to killing someone who is barehanded and with no defenses.
1. Hammer. A decent sized hammer can break their bones and smash their skulls, rendering them incapable of attacking you.
2. Swords. Slice and dice through the masses.
For ranged, it would depend on how skilled you are with various weapons. It's partially a matter of capability and skill, and also practicality and effectiveness.
1. Bow and arrow. This is deadly, but can be difficult to use and also arrows are bulky and difficult to bring around.
2. Guns. Bullets are easier to bring, but are loud and attract attention. There is also the chance of misfiring because of recoil, etc. and the weapon itself malfunctioning.
3. Spears. Uhm, no.
4. Slings. Useful, but not strong enough.