Evasion

You can avoid even magical and unusual attacks with great agility. If you make a successful Reflex save against an attack that normally deals half damage on a successful save, you instead take no damage.

Evasion can be used only if wearing light armor or no armor. A character who is paralyzed, held, bound, sleeping, unconscious, or otherwise completely at an opponent’s mercy does not gain the benefit of evasion.

Rogues get Evasion as a class feature at Level 2, Rangers at Level 9.