[@GingerBoi123] Seems to me like you'd want a stupidly-oversized version of the Lancer from Gears of War- a big gun with, effectively, a chainsaw "bayonet."

[img]http://www.projecttriforce.com/images/products/secondary/gow_gun-1.jpg[/img]

Something like this, would you say? Except scaled-up to anti-tank rifle size.