Adrenaline Rush is an ability available as a talent in the rogue's Combat tree. It instantly increases your energy regeneration rate by 100%, effectively enabling the user to use energy-heavy abilities almost without pause.
Tips and tactics
In raid situations, try to save up your adrenaline rush if you're close to fighting a boss. Adrenaline Rush and Blade Flurry (another ability in the combat tree) are incredible tools for improving your burst DPS. Remember to let the tank get some threat before using this, as this can easily lead to overaggroing.
When soloing, try to use your Adrenaline Rush early on in fights — you have a much better chance to keep your target stunned and make full use of your buffs at the beginning of a fight than at the conclusion. Using AR along with Blade Flurry with Evasion and one's favorite damage moves allows the rogue to survive multiple-opponent fights that would otherwise necessitate vanishing or using sprint to retreat.
Patch 3.1.0 (14-Apr-2009): Cooldown reduced to 3 min. Was 5 min.