The Melta Cannon is fairly plain, but the version created for the Forge World Reaver Titan looks rather cool, so I thought I'd have a go at improving the stock version.
Apart from the arm, which I made from plastic rods of various sizes, there are three new additions. First is the piping on the back - this is from the arm of a 40K scale Necron Destroyer (the arm is discarded when you upgrade to a Heavy Destroyer). Second, I've added the muzzles from a Necron Immortal's Gauss Blaster to the front of the gun.
Finally, the underslung piping and housing is from the powerfist of a Space Marine Terminator.
Here's the Melta Cannon, attached to the main body of the Titan:
