As a brother of the Unforgiven, my weapon of choice is the Plasma-cannon, with the trusty bolt-pistol.
When I aint in me trukk or on me bike, I'll probably tote around a big wrench to knock some gits around, maybe a powerklaw if I'm feeling nasty. As for me shoota, probly a real snazzy kombi shoota-skorcha
As a Dark Apostle i should be wielding my holy Crozious. However this is unlike to be added because its an artifact meant for the sacred hands of only a few religious fathers of the Word Bearers. I think a power maul , or a two handed chain-axe would deliver the proper reward to the infidels and the xenos. As for long range , the sight of a plasma cannon's blast that turns flesh to ash is something that captures my attention. I am bound to play in melee but if there is an option for some explosive attitude , i will also try it.
Give me a power scythe, or a corrupted thunder-hammer and storm shield. I want to stand in the face of my enemies and crush them beneath my fetid bulk as I stride across their shattered, twitching bodies.
Assault jump pack, Dual weild power chain axes and a plasma pistol would allow me to cut through many enemies before going down... or going up An assault jump pack with a thunder hammer could cause massive AoE damage if used correctly!
Space Wolf: Runic armor, Stalker pattern Bolter, Frost Blade (Sword or Axe, either or, y'know) Eldar: Executioner, Shuriken pistol, so on so forth. Chaos mehreen: REAPER M-FING AUTOCANNON Ork: So... much DAKKA!!! Twin-linked Shoota, for more Dakka. The ability to loot a space wolf frost blade (It fits my army's story, deal) 'eavy armor, with all the spikey bitz. Also, Gretchin. I need my Gretchin.