Nothing here is a 100% drop just a higher then normal chance.
Assault Rifles
Madhouse - Mad Dog, Lynchwood
Veruc - Mobley, The Dust
Hammer Buster - Old Slappy
KerBlaster - Midge-mong, Southern Shelf
Shredifier - Bonehead 2.0, Arid Nexus
Pistols
Gub - Laney, The Fridge
Hornet - Knuckledragger, Southern Shelf
Maggie - Mick Zafod, The Dust (Side with Hodunks)
Thunderball Fists - Captain Flynt, Southern Shelf
Gunerang - Rakk Man, The Fridge
Unkempt Harold - Unknown
Infinity - Doc Mercy
Logan's Gun - Wilhelm
Rocket Launcher
Badaboom - King Mong, Eridian Blight
Pyrophobia - The Warrior / Possibly Incinerator Clayton too
Norfleet - Unknown
Bunny - Chubby enemies
Nukem - Black Queen, The Dust
Mongol - Dukino's Mom, Lynchwood
Shotguns
Conferance Call - The Warrior
Striker - Unknown
Deliverance - Tumba, Wildlife Preserve
Flakker - The Warrior
Sledge's Shotgun - Smash Head, The Fridge
Sniper
Pitchfork - Terramorphus
Invader - Saturn
Skullmasher - Son of Mothrakk, Wildlife Preserve
Volcanoe - The Warrior
Lyudmila - Gettle, The Dust
Longbow - Badass Creeper, Caustic Cavern
White Death - Mobley, The Dust
SMG
Slagga - Hodunk, The Dust
Emperor - The Assassins, Southpaw Steam & Power
Bitch - The Warrior, BNK3R?
Hellfire - Scorch, Fropstburn Canyon / The Warrior
Baby Maker - Madame Von Bartlesby / Mad Dog, Lynchwood
Shields
The Transformer - Pimon, Wildlife Preserve
Whiskey Tango Foxtrot - Chubby Enemies
The Sham - BNk3R
The Bee - Hunter Hellquist, Arid Nexus Badlands
Fabled Tortoise - Blue, Caustic Caverns
Black Hole - Foreman, Opportunity
Impaler - The Warrior?
Neogenator - Spycho, Frostburn Canyon
Grenades
Bonus Package - Bewm, Southern Shelf
Bouncing Bonnie - Loot Midgets
Fastball - Boll, Three Horns
Fire Bee - Unknown
Leech - The Warrior
Quasar - Ultimate Badass Varkid
Rolling Thunder - Old Slappy
Storm Front - Rat Brothers, Bloodshot Stronghold
Got nothing on legendary class mods or relics
? after bosses name is if it's unconfirmed still, and another boss possibly drops it.
*I got this posting on the gearbox forums*