Keep in mind more weapons may become available.

Bow & Arrows: Does 6 hp worth of damage (arrows are not returned)
Boomerang: Does 2 hp worth of damage (returned)
Mace: Does 2 hp worth of damage (hold on to)
Sword: Does 3 hp worth of damage (hold on to)
Throwing knife: Does 3 hp worth of damage (person attacked gets knife)
Grenade: 15 hp of damage no matter what in space it is thrown
Shield: Protects you from 1 hp of damage (does not protect from grenade)
Hand-Hand Combat: Person with most health points comes out on top and does 1 hp worth of damage
Rock: 2 hp worth of damage (stays with tribute)
Knife: 3 hp worth of damage (stays with tribute)
Mine: Does 7 hp worth of damage to the tribute who steps on it and 3 hp if in the space right on edge of mine (determined by person who set it)