For PvE? No question, it is Skyburner's Annex. I say this for 3 reasons: 1. Against bosses and strong enemies, you are likely doing the bulk of your damage with a special weapon; 2. Outside of bosses during damage phases, a nightstalker's core responcibility is to generate orbs and enable quick elimination of tougher targets (both of which come from using Shadowshot); and 3. The exotic is self-sustaining and synergistic with basically any nightstalker build. With a 25-30% activation rate, Skyburner's Annex allows you to generate orbs while your super is down while also drastically improving your super energy gains when you get Heavy kills. This can result in double-dipping orb generation during add phases of bosses as a heavy weapon kill will activate both Light of the Pack and the perk on Skyburner's Annex. A group of about 6-8 enemies will almost fully restore your super if you use it to clear a pack. Going one step further, since most orbs tend to get wasted during strikes as they are left behind, this enables you to collect those orbs for free special ammo. For bosses and difficult enemies, this can prove to be an invaluable asset since you may not be able to run out and grab ammo boxes (assuming there are any to pick up). While this may not be a mainstay idea, this added flexibility does make it easier to approach situations.

Bones. Duh.

Crest for orbs and fast res Sealed Grasps for double smokes Bones for movement ability