Fallout: Brotherhood of Steel secret weapons

There are three "secret weapons" in Fallout: Brotherhood of Steel: the Meat Cannon, the Slugger, and the Shredder. They are roughly the equivalent to the "unique weapons" that are found in Fallout 3.

Meat Cannon
The Meat Cannon is one of the most powerful weapons in the game, and be obtained very soon in the game if you know where to look. Beware, if you equip it, you can not dodge. With a few modifications, this weapon uses pre-loaded explosives bathed in blood and so it needs no ammunition. It shoots five explosives at the same time and causes considerable damage to anyone standing near the impact point, even the player.

Location
To find this, you must leap into the dark void just to the east of the last savegame terminal near the level's exit. You will not die and you must continue straight on towards of a destroyed bridge. A little farther from it, kill all ghouls and loot the footlocker toward the ice cream truck.

Slugger
It's a very powerful weapon for Chapter 2 and remains very good even in Chapter 3. It has powerful critical damage, and every critic, the enemy eject very far. Despite these characteristics, in Chapter 3, there are better melee weapons.

Location
Docks of Los, found on the secret Giant Glowing Ghoul's corpse. To get it when you're on the Docks Shipyard, check all of the alleyways north of the large area of radioactivity until you find a couple of glowing ghouls standing behind an unscalable fence. They cannot be reached by standard weapons, but you can hit them with explosives or another weapons like Incendiary Mortar. Kill these ghouls and the Giant Glowing Ghoul will spawn just outside the alley's entrance. After, you need just kill him and he drops the Slugger.