Instantaneous Rage

(Masters of the Wild: A Guidebook to Barbarians, Druids, and Rangers, page 23, DnD 3.0)

[General]

You activate your rage instantly.

Prerequisite

Ability to rage

Benefit

Your rage begins at any time you wish, even when it's not your turn or when you're surprised. You can activate your rage in response to another's action after learning the result but before it takes effect. Thus, you can gain the benefits of rage in time to prevent or ameliorate an undesirable event. For example, you can gain the additional hit points that rage grants just before a blow that would otherwise cause you to tall unconscious or better your chances of making a successful saving throw against an incoming spell.

Normal

You enter a rage only during your turn.