The Katana is not unique. Yes it’s an awesome weapon, but this guide is for items SO rare, there can only be one! (see what I did there?)
It’s true, look! http://fallout.wikia.com/wiki/Katana_(GRA)
This guide contains content from Gun Runners’ Arsenal, detailing all the Unique Guns, Energy, Melee and Unarmed weapons and their enjoyable effects.
MF Hyperbreeder Alpha (0:58)
Greased Lightning (1:39)
Two-Step Goodbye (2:23)
Medicine Stick (2:50)
Nuka Breaker (3:49)
Embrace of The Mantis King! (4:18)
Li’l Devil (4:36)
Cleansing Flame (4:53)
Sprtel-Wood 9700 (5:19)
The Smitty Special (5:36)
Let me repeat myself, the Katana doesn’t qualify as a unique so it wasn’t included.