Cutthroat's rebuke
rogue attack 23
Melee weapon
Requirement: wielding a light blade.
Target: one creature
Attack: Dexterity vs. AC
Hit: "4[W] + Dexterity modifier damage."
Ruthless Ruffian: This power gains the rattling keyword.
Effect: The next time the target makes a melee attack against you before the end of your next turn, you can make a melee basic attack against it as a free action. If your melee basic attack hits, you knock the target prone.[MP2:69]
Cutthroat's rebuke is an encounter power available to rogues at 23th level.
It is a weak choice for character optimization, being a version of riposte strike that does slightly more damage but still has problems with the core function of the power. [Charop rogue]