Fallout: Brotherhood of Steel secret weapons

In Fallout: Brotherhood of Steel, there are three secret weapons: the meat cannon, the Slugger and a special version of Red Ryder BB gun. They are roughly equivalent to the unique weapons in Fallout 3, at least in case of the meat cannon and the Slugger.

Meat cannon
The meat cannon is a unique incendiary mortar.

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.
 * Los Bridge East, Found in footlocker on hidden island.

Red Ryder BB gun
This special Red Ryder BB gun is a unique version of standard Red Ryder BB gun.

Thanks to his high knowledge in repair, the Vault Dweller has modified a Red Ryder BB Gun for it absorbs and propels the surrounding air, forming a ball of air, so it needs no ammunition. But since the air is a hard to control, its damage is changing and may be very low or very powerful.

Location
This weapon is given to you by the Vault Dweller upon successful completion of the quest Rescue Innocents with the most innocent saved (37).
 * Carbon Warehouse Main Storage, Given to you by the Vault Dweller if you save all the survivors of the raider attack on Carbon.

Slugger
The Slugger is a unique spiked baseball bat.

It's a very powerful weapon for Chapter 2 and remains very good even in Chapter 3. It has powerful critical damage, and every critical hit knocks back your enemy a good distance. Despite these characteristics, in Chapter 3, there are better melee weapons.

Location
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. Then, after you kill him, he will drop the Slugger.
 * Docks of Los, found on the secret giant glowing ghoul's corpse.