I remember that Marvel showed a physical torpedo in one of it's comics.

I think it's when the bounty hunter Valance is remembering his origin story as a stormtrooper left for dead after a Rebel attack (can any Marvel collectors help me out here?).

If memory serves it looked a bit like an elongated vacuum valve (presumably the proton glow activated when the target was near).

I thought it looked rather cool at the time and was pleased it was a physical object and not another energy weapon (proton torpedo as in neutron bomb).