Probably the T-45 in my opinion. I know, kind of standard, but I just love the design plus the nostalgia it brings. T-60 is good, but a bit too bulky for me.

The original Enclave Armour of course. You'll never see a power armour quite like it. It's sleek and bird-like in appearance, while also having an intelligent verisimilitude to the design. No pointless nuts and bolts hanging out of this baby for "coolness"s sake.

It was a toss up between that and the t-51, which is another gorgeous looking armour.

I'll be honest, I get that people like the t-60 but it's disappointing to me that it's just a revamped version of the t-45.

I like T 45D, T 51B and Enclave armor from fallout 2 and New vegas

Definitely the original APA. New Vegas didn't seem to give it justice - in 2 it literally towers over you, very intimidating and mysterious. Probably T-51 behind that.

Also, I know this is offtopic, but wouldn't it make more sense for Advanced Power Armor MkII from Fallout 3 to be in 4, considering the geographical closeness of the Capital Wasteland to the Commonwealth? (in contrast to the West Coast Enclave).

I liked the Scorched Sierra armour. I didnt like the fact you had to nuke the NCR to get it, thankfully, there's the console

Tribal power armor, as much as i like the apa theres something about wearing a skull as a codpiece that makes you feel in charge.  

I'm not a big fan of power armour, but the T-51b looks nice.

The scorched sierra power armor is my favourite since it's unique and stands out among the other power armors. Just a shame that you need to blow up the NCR if you want to obtain it.

The Tribal power armor from The Pitt DLC.

Looking back at it, The Pitt was probably the only thing I really liked about 3.

This was tough. As far as looks, here's my top five:

1st: T-45
2nd: T-60
3rd: Advanced Power Armor MkI
4th: T-51
5th: Ashur's/Tribal Power Armor

*Where's the Midwestern PA & Ashur's?

My favorite power armor will always be the original T-51 and it's variants. One of the most powerful power armors, it was the pinnacle of pre-war infantry technology(Yes, I know Bethesda messed with that). I really love it's tank-like design and just how iconic the armor is, being on the cover art of the first Fallout game.

My close second is definitely the Advanced Power Armour Mark I, the original Enclave armor. It is one of the coolest looking Armors ever and in my opinion, the most intimidating.

In my first place would be Advanced Power Armor Mk II, in second place T-51 and in third place T-45.
Advanced Power Armor Mk II had intimidating visuals and looked just cool.

I just love power armors in general, but my absolute favorites are that of the Enclave. Especially the Enclave Hellfire power armor, its just so big and menacing.