I'd totally be down for your character having a giant drill. That even adds a nice touch to your silhouette. Or maybe you can think of a cool transformation where different parts of your armor come together to make it. 

Breaking immersion every time you use your killer weapon as I am forced to think of Tengen Toppa Gurren Lagann, is not what I want from Deathwatch, personally. :P

Comedy doesn't have to rely on "heh, lulzy, I break the setting, but it's ok, because comedy".

*note, I am not the GM, so you don't have to take anything I say seriously.