Riposte is a 10-Energy attack based on weapon damage. To use this ability, you must have recently parried an attack. This ability can be used on an enemy that wasn't even parried by you.
Lethality increases the critical strike damage bonus of your Riposte by 6%, 12%, 18%, 24%, or 30%.
Requires you to have recently parried an enemy's attack, which means that the enemy must be hitting you.
Tips and Tactics
Riposte is most useful against warriors, hunters, paladins, and other rogues; slowing their weapons takes most of their bite away.
You cannot create macros that automatically check for buffs or debuffs on a target and change abilities accordingly, but you can create a macro that will randomly choose between your main attack and Riposte, like so:
/castrandom Sinister Strike, Riposte
Useful in solo leveling, since it's pretty cheap (10 Energy) and lets you take advantage of the +6% parry chances.
The Floating Combat Text inteface options can be set to display a message when Riposte becomes usable.
Patch 3.0.3 (04-Nov-2008): Duration of this effect no longer reduced by other effects that reduce disarm duration.
/Patch 3.0.2 (14-Oct-2008): Now slows the target's melee attacks by 20% instead of disarming them, awards one combo point.