Still the Ghostblade. Not the biggest hitter, but 1 weight, ignores armour, and it's see through. Can't go wrong.
I only found the Ghostblade a few days ago so I've spent some time beefing it up a bit so I can use it on master, I've got it up 134 damage now so it's more than strong enough to play with, when I get one-handed upto 100 with all the perks it might hit 200 (without farting around with alchemy loops and things) then I'll probably switch it out with something else at that point.