I'm a big fan of Nightingale armour myself - it just looks so awesome. I quite like the look of the Penitus Oculatus (sp?) armour too, and (for most characters, at least) General Tullius's armour is so badass it hurts. Problem is though, I have to side with the Stormcloaks to do that, and I'm an Imperial guy. :(
Wolf armour goes pretty well with Dawnbreaker, oddly enough; for full sets, Dwarven looks quite good (not a huge fan of the helm, though).
On the other hand, you've got stuff like Dragonbone and Daedric, which (though yes, they do look badass) would probably slice your arms off in actual combat. (check http://tsoalr.com/?p=111 out for an example). Not quite to my taste (cause I want arms and all) but I must admit, they do look pretty awesome.