Steel Plate armor with the full face helm is hands down my favorite heavy armor in the game, un-modded.
A near second is Wolf Armor, I use a mask rather than that helm though.
For light armor, it depends a lot on the gender and race.
Some characters look pissa wicked in Glass, some hulking male Nords, Orcs & Redguard look mean in Hides & Furs, all of which can exceed the soft armor cap of 576 with full 100 Smithing & Light Armor perks.
Stealthy types look sweet in the DB Shrouded stuff, as well as Thieve's Guild, Limwe's set and Nightingale duds.
On a PC, I use a mod that makes all Elven items blackened with gold highlights and it looks amazing!