Most creatures have natural attacks. You can use the Unarmed Attack skill to strike with your fist or another body part, calculating your attack and damage rolls in the same way you would with a weapon.
All unarmed attack and natural weapons belong to the Unarmed weapon group.
Unarmed attacks and natural weapons do not count as weapons for the purposes of effects and abilities that work with weapons unless otherwise specified.
Some creatures, most notably humans, do not have natural weapons, and instead have unarmed attacks. These attacks function much like natural weapons, but they only do nonlethal damage, and the attacker is not proficient with these attacks unless they have the necessary training (as represented by the Combat Martial Arts feat).
Natural weapons cannot be disarmed, though targeted strikes may damage the limb to the point where they cannot be used.
The weapons below are all for a Size 5 creature. Adjust the damage dice and size of the weapon as appropriate for creatures that are larger or smaller. Some creatures, due to supernatural powers or enhancements, do more than the standard damage for a weapon of their type.
Humans, including supernaturals in human form, possess only the Unarmed Attack natural weapon, representing punches, kicks, headbutts, elbows and other strikes a human can make with their body.
NOTE: Natural Weapon bulk only applies for abilities that rely on weapon bulk. A natural weapon does not count against its wielder's carrying capacity.