Once you reach level 50 and have chosen a Build for your Rogue, you will want to start picking out the best weapons to complement it. The weapons or Legendary Aspects are designed to enhance either a specific Skill, a group of Skills, or your overall damage. Some of these will be best for a specific Build, but many will be good for most, if not all Rogues.
Best Rogue Weapons

Skyhunter
(Bow)
Guarantees that the first direct damage you deal to an enemy is a Critical Strike. Also increases a Skill’s Critical Strike Damage and grants you energy when it uses stacks of Precision.
Best Build: Any
Gives an overall damage boost while also helping keep your Energy high.

Condemnation
(Dagger)
Makes your Core Skills deal more damage when spending 3 Combo Points, while also giving Basic Skills using this weapon a chance to instantly generate 3 Combo Points.
Best Build: Rapid Fire Build and Penetrating Shot Build
Allows you to use your Primary Skill with 3 Combo Points much more, while boosting its damage.

The Umbracrux
(Dagger)
Your Subterfuge Skills create a Shade Totem that can be attacked. Any damage it takes is partially replicated to surrounding enemies.
Best Build: Penetrating Shot Build
Gives you an extra source of area damage.
Best Rogue Legendary Aspects

Repeating Aspect
(Offensive Aspect)
Gives Rapid Fire a chance to ricochet to another target
Best Build: Rapid Fire Build
Lets your primary Skill attack more enemies.

Aspect of Retribution
(Offensive Aspect)
Gives you a chance to Stun Distant enemies when they hit you. Also increases your damage against Stunned and Knocked Down enemies.
Best Build: Barrage Build
Gives you some extra damage and survivability.

Aspect of Retribution
(Offensive Aspect)
Increases your damage while you have a Barrier active.
Best Build: Barrage Build
Gives you an overall damage boost.