The Gunslinger Coat is a Jacob Frye outfit that raises firearm damage by 20%, styled as an outlaw's coat cut like an Assassin's.
Pick it when a fight is likely to be settled at range. The +20% applies only to firearms, so it does nothing for brass knuckles, cane-sword or kukri damage, and you lose the stealth or defence bonuses that other outfits give.
Aveline (Evie)
The Aveline outfit gives Evie Frye the look of Aveline de Grandpré and adds three to each tool capacity. It comes from the Ubisoft Club.
Ballgown (Evie)
The Ballgown is the formal dress Evie Frye wears to infiltrate the Queen's ball.
Baron Jordane's Finery (Jacob)
Baron Jordane's Finery is an upper-class suit for Jacob Frye that lets him carry three more of each tool: throwing knives, hallucinogenic darts, smoke bombs and voltaic bombs.
Blackguard's Suit (Jacob)
The Blackguard's Suit is a dark blue and black Jacob Frye outfit that cuts the melee damage he takes by 20%.