Might be cheating here but Thunderfire cannon? If not that then dual wrist mounted flamers and a thunder hammer.

Ah, an Imperial Fist... You still love to get toe-to-toe with your enemy eh?

I'm a Templar at heart, are the sons of Caliban not given to righteous close combat?

I am favoring a thunder hammer, just as you do brother templar. I love to see the light snuffed out of my enemies' eyes

That sounds scarily awesome. Not only can you shoot psy-death you can shoot Heavy Bolter death while cracking skulls.

As for me, Plasma-anything, Flamer-anything, Powerfist/Sword/Hammer.

My favorite SM weapon? The one that malfunctions so i can get the chance to get in close range with my chainaxe

To those saying the Thunder Hammer.

One-handed or Two-handed variants?

Either to be honest, but if I get a Thunder Hammer I'll more than likely will go with the two hand simply for the "Oh Sh*t!" factor the enemies will feel when I storm in to their ranks.

@Hrolgard Power fist is nice to be sure, but in game terms it is too slow and cumbersome...practically it would also be slow and cumbersome. If Im going into melee, it would depend on whom I am facing. Toss up between paired wolf claws or Thunder Hammer (Always one handed...need the shield to counter the slow swing to block with) and Storm Shield. For ranged, Im a fan of Plasma Guns or Sternguard Bolters.

The bolt pistol.
Simple yet effective.