a changeup of the old-school rifle that makes it an armor-piercing Rail Driver.
all the stuff a rail driver has, shoot through bricks, blue-ish muzzle flash and hit emitter, all that blarg.

sorry i couldn't make it bigger,
and make a transparent thing that can see through bricks like looking through a feather so you can do this:

oh, and in red faction, if you fire a rail-driver it goes BLEWM!! and you open it like a break-action shotgun, but there's no shells.
also two blue ligts pulse up and down the barrel, you could probably simulate that by using a .gif as a texture.