Obviously it depends on what character you are playing, but personally I love Graham's armor, elite riot armor and the sierra power armor <3
I think pretty much all of the Ranger armors look and are badass as hell.
Elite Riot Armor is awesome looking and a decent compromise between power armor and combat armor MK 2.
Power armor has a great protection. Looks like a tin can suit of armor, however.
Joshua Graham's armor or Sierra Madre armor when using the Light Armor perks.
Stealth Suit Mark II otherwise. Just recently used the Elite Riot Armor for the first time, it worked pretty well so I may start using it more.
My characters usually end up in some kind of combat armor. With Boone's Beret and Authority Glasses.