Thump-Thump is a unique grenade rifle which has the extended range of a barrel extension mod found in its common counterparts and enhanced AoE radius. It also has a 30% faster attack speed, 0.5 lower weight, and is 25% more durable compared to a standard grenade rifle. It also has a unique texture and the words "Thump-Thump" scrawled on the side with an arrow pointing towards the muzzle. There is also a drawing of an angry beaver with red eyes holding a rifle on the stock. Standard 40mm grenades fired from this weapon will have twice the velocity as ones fired from other grenade rifles.
If the Boomers are killed for Mr. House or Caesar's Legion before obtaining the Nellis generator key from Raquel, Thump-Thump cannot be obtained. The building's door is unpickable and can only be opened with the key, which does not appear on her body if she dies.
Thump-Thump uses a unique projectile to give it the projectile speed bonus, meaning said bonus only affects standard 40mm grenades.
Even though Thump-Thump has increased attack speed over a normal grenade rifle, it doesn't have increased reload speed, largely mitigating the DPS boost.