Gouge is a level 22 Outlaw rogue ability that incapacitates the target for a short period of time. Once a successful Gouge has been made, any damage will negate its incapacitation effect. Note that using Gouge will automatically turn off auto attacks.
Gouge's short incapacitate is the main reason for using the ability, allowing one to perform a quick bandage, or getting a few seconds to distance yourself and get out of combat.
Gouge's effect breaks upon receiving damage; this means that it does not work well in group combat unless well-coordinated. However, in all situations Gouge is useful as an interrupt. If [Kick] is on cooldown, Gouge can be used just for the purpose of interrupting a spellcast.
Tips and tactics
Gouge gives you an opportunity to apply a bandage, recover energy, or plan a quick escape. Also note that during those 4 seconds one can recover up to 40-60 energy, so it can be seen as a free combo point anyway.
Facing multiple enemies can be quite difficult. Simply Gouge one. This will give you time to finish one of them. This will greatly reduce the amount of incoming damage.
In end-game raiding, Gouge has proven useful in interrupting caster enemies if they are immune to stunning with [Cheap Shot] or silencing with [Kick]. It may be expensive energy wise, but it will at least buy time and prevent extra damage to your fellow raid members.
Patch 7.0.3 (2016-07-19): Now available only to Outlaw and awards 1 combo point. No longer requires the target to face the rogue.