Being a Salamander at heart, the only weapon I truly want to take into battle is the Spear of Vulkan. Oh, and maybe the Gauntlet of the Forge too, because who doesn't want a wrist mounted flamer.
power claws (the finger type)/ or chain glaive, lacking those two the helmet of a loyalist, but hey you always find those lying around.
Even though I too consider myself a fan of the Salamanders, I must say that I would prefer a heavy bolter and let the Forgefather have the honour of wielding the artefacts of Vulkan himself.
Ah, yes, of course, i was just talking hypothetically. If I were restricted to things available to a normal space marine? I would have to go with a trusty vulkan pattern combi-flamer, and a combat blade artificed and adorned with the marking of the promethean cult. Man I love the vulkan pattern. EDIT: Changed Melta to Flamer, thanks other poster that mentioned it!
Back when I was playing Space Marine I enjoyed using the heavy bolter quite a bit. I think it will be the same in this game.