I'm quite a fan of both the Merc Troublemaker and Adventurer outfits in the vanilla game, but if I need to get properly armored, the Riot Gear from Lonesome Road tends to be my go to.

A difficult one as I have quite a few favourites. Power Armour would be the Outcast variant of the T-45d, Medium armour as with most would be the Riot Gear, and light armour would be either an armoured vault suit or the Wanderer's leather armour.

If I get mod access I'm planning on getting the Sith Stalker armour, as even though it's something out of Star Wars it still looks somewhat lore friendly.

Spoiler:

My favorite armor is wasteland wanderer outfit.

My first char prefers light and usable armors, I play mostly in recon armor. Another one is BoS Knight, so he wearing Power Armor.

My favorite armor is the elite riot armor from lonesome road, it's pretty awesome version of the desert ranger armor.

Vanilla - Chinese Stealth Suit
Mod - Reinforced Chinese Stealth Suit, lol...

My favorite vanilla armor is probably just the Assassin armor from DM, my favorite mod armor however is Drag's Deathstroke armor. By far the best I've ever found.

From New Vegas its got to be NCR Ranger Combat Armor all the way from the jacket, body armor and helmet it all looks stunning and very apocalyptic

From vanilla Fallout, my favorite was the Wasteland Doctor outfit. It was like the merc, but it's a litlte bloodied, has a couple tactical attachments, and looks to be easy to move in. I just always kept a set of power armor in my inventory in case I ran into trouble and needed protection. This was my strategy in both FO3 and NV.

Once Dead Money was released, the assassin's armor took my #1 spot.

Then, once Honest Hearts was released, Joshua Graham's armor took over. It was a perfect mix of aesthetics, baddassery, and lightness.

I could never get into the heavier armors because they slowed me down too much. Otherwise I would have liked the ranger vet armors a lot more. But, in general, those armors were too heavy to walk around in, and too light for fighting deathclaws.

Vault Scientist outfit/armor. Some of my favorite screenshots from the early days of Fallout 3 playthroughs have that armor in them.

Simple the Veteran Ranger armor from the NCR. I was gonna go for the Brotherhood of Steel T-45D armor, but I think the Veteran Ranger looks cooler. I thought it was so cool I added it to my Fallout 3 game.

Armor Joshua Graham's closer to the heart.

Elite riot gear from Fallout:NV

It would have to be Joshua Graham's armor. It was really the only armor that stood out above the rest.

Favourite None Mod Armor: Fallout New Vegas Honest Hearts DLC Daniels Outfit, I just like the casual feel of it and when I walked the wasteland with it and a backpack mod and a raider belt from the tailor maid mod it just feels and looks awesome..

Favourite Mod Armor: Hmm to many to say.. though I guess I like Dragbodys Rick Grimes outfit.. though I am yet to be able to wear it on my character so we will have to see..

Armored jumpsuits...cause it was the coolest thing I ever unlocked in a game back in fallout 3, and still might be. But how cool was it to be the "Death dealing blue condom road warrior" that you were???

I like enclave armor since fallout 2, but in nv the elite riot armor design is more awesome.

Ranger Combat Armor because NCR. When it comes to mods Kerberos Panzer Police. I really need to see Jin Row.

Combat armor like the one of gun runners guards remember me the colonial marines of aliens

Joshua Graham armor and desert ranger armor.DLC Honest Hearts