Firefly is a trait in Destiny 2 that can appear on 55 weapons. There is also an enhanced version with a stronger effect.
What Firefly does
Precision kills with this weapon increase reload speed and cause the target to explode, dealing Solar damage to nearby enemies.
Enhanced version
Precision final blows with this weapon substantially increase reload speed and cause the target to explode, dealing Solar damage to nearby targets.
Weapons that can roll Firefly (55)
Ace of SpadesKinetic · Hand Cannon
The Jade RabbitKinetic · Scout Rifle
Accrued RedemptionKinetic · Combat Bow
AgapeSolar · Hand Cannon
All or NothingStrand · Pulse Rifle
Belisarius-DStrand · Pulse Rifle
Blast FurnaceKinetic · Pulse Rifle
BygonesKinetic · Pulse Rifle
Circular LogicStrand · Machine Gun
Conspiracy HonedStasis · Sniper Rifle
Corrective MeasureVoid · Machine Gun
Corrective Measure (Timelost)Void · Machine Gun
Corundum HammerStrand · Hand Cannon
Crimil's DaggerKinetic · Hand Cannon
Defiance of YasminKinetic · Sniper Rifle
Defiance of Yasmin (Harrowed)Kinetic · Sniper Rifle
Doom of ChelchisVoid · Scout Rifle
Doom of Chelchis (Harrowed)Void · Scout Rifle
EyaslunaStasis · Hand Cannon
FatebringerKinetic · Hand Cannon
Fatebringer (Timelost)Kinetic · Hand Cannon
Hung Jury SR4Kinetic · Scout Rifle
Hung Jury SR4 (Adept)Kinetic · Scout Rifle
ImminenceStrand · Submachine Gun
Imminence (Adept)Strand · Submachine Gun
Last RiteKinetic · Scout Rifle
Midnight CoupKinetic · Hand Cannon
Modified B-7 PistolStasis · Hand Cannon
NullifySolar · Pulse Rifle
Nullify (Adept)Solar · Pulse Rifle
Opaque HourglassArc · Combat Bow
Peculiar CharmKinetic · Submachine Gun
Praedyth's RevengeKinetic · Sniper Rifle
Praedyth's Revenge (Timelost)Kinetic · Sniper Rifle
Qullim's TerminusStasis · Machine Gun
Qullim's Terminus (Harrowed)Stasis · Machine Gun
RelentlessStrand · Pulse Rifle
Relentless (Adept)Strand · Pulse Rifle
RoseKinetic · Hand Cannon
Sacred ProvenanceKinetic · Pulse Rifle
Smite of MerainKinetic · Pulse Rifle
Smite of Merain (Harrowed)Kinetic · Pulse Rifle
Solemn RemembranceStasis · Hand Cannon
The MartletVoid · Pulse Rifle
The Ringing NailSolar · Auto Rifle
The ScholarStrand · Scout Rifle
The Spiteful FangStasis · Combat Bow
The Time-Worn SpireStasis · Pulse Rifle
UnworthyArc · Scout Rifle
Veles-XVoid · Pulse Rifle
Vikala SMG4Void · Submachine Gun
Vision of ConfluenceSolar · Scout Rifle
Vision of Confluence (Timelost)Solar · Scout Rifle
Zaouli's BaneSolar · Hand Cannon
Zaouli's Bane (Harrowed)Solar · Hand Cannon