It really depends on the guy I'm playing to tell the truth.
Warrior wise if I go with heavy armor I really like the regular steal armor with the shoulder plates (not steal plate), the kind Farkas wears. And I also like the Blades armor (torso piece at least) and the Wolf armor is cool except it looks like the textured over a basic design without really putting the coding effort into making it look as detailed/3D as other armors.
Thief wise, the nightengale armor is pretty cool; but I go tired of that. I like Linwe's armor for my ranger type character. And I use the Guild master armor for my "adventurer" type guy because I wanted him to look like a traveller: pouches and stuff. (I really wish I was on the PC, I'd totally get the assassin' creed mod for the thieves guild armor (not the one for nightengale) because it actually looks like a detailed piece of clothing with different colors than just the black/brown or gray I have to choose from now. Fits the "adventurer" guy more.
Other than that I have armor that to me works specifically for certain characters I have (and I don't like them as much on others) -- My argonian warrior with dragonscale (no helm) look awesome. My Khajiit in Savior's Hide with Foresworn boots and bracers looks awesome.
To be honest I really feel like Bethesda dropped the ball on the armor, there is a lot that doesn't mix and match as well as it could if they paid attention to that. i'm not saying it should all mix and match perfectly, but some instances it would have really expanded the options for player customization. And just certain pieces of armor are kinda 'meh' IMO. The orc armor is neat, but it would be nice to have an option to remove the shoulder spikes (kinda like there are two steal armor pieces), the orc boots look kinda dumb with the turned up toes and the green shield should match the armor color, not the weapon color (though I wish all the orc weapons were that steal color of their armor and not that green. The glass armor is a bit too gaudy, if they toned it down some it would have been great; and the mod I saw online of a silver/bluish version was much better than the green/gold. The elven armor is a bit too leafy. And the Ancient Nord Armor - an awesome armor set that is totally ruined by the main piece that has jack crap covering the legs. It looks really stupid having all that armor on and not even a piece of leather covering your legs (b/c it's split on both legs).
