"Vengeance" Gatling laser - Deathclaw Sanctuary ; far in chamber, blood grotto.
"Wazer Wifle" Laser Rifle - Little Lamplight ; Persuade Biwwy to sell it to you.
"Victory Rifle" Sniper Rifle - Abandoned shack ; in a shack locker north of the rockbreaker's Gas Station.
"The kneecapper" Sawed- off shotgun ; Girdershade, carried by Ronald Laren.
"Experimental MIRV" Fat man - National guard depot ; in the Armory and Bunker
"Miss Launcher" Missile launcher - Fort independence ; southwest room on lower level.
"A3-21's Plasma Rifle" Plasma Rifle - Given as reward for completing quest: The Replicated man.
"Eugene" Minigun - Reilly's rangers compound ; reward for quest: Reilly's rangers.
"Burnmaster" Flamer - Flooded metro ; inside a trap-filled storage chamber.
These are not all of the special weapons, just the best of them.