Henkei by far. Taking the original concept and turning into an awesome toy. I dont dislike the colors of the Classics one, but seeing it done in the G1 colors just perfects it.

 

Honorable Mentions to TM and TM2 Megatrons from BW, though they're not on the poll

Honorable Half-Mention to Movie Leader (Premium). His robot mode is absolutely fantastic.. if he... transformed.. into... well... anything, he'd probably be my favorite, but his alt mode really isn't very well executed at all.

Steroids could make you grow a pair of scarab horns?! :nooo

If he'd read the warning label before taking them he wouldn't be in his current situation :D

 

Though I removed the horns from him once just to see how it would look, and I have to say I prefer the horns on.

Haven't seen TFA: Leader yet.

Voted MP-5

really nice figure.

I'm a fan of Dragon Megatron

Animated Earth Mode Megatron FTW - Menacing, full of character, excellent deco and an overall good design and solid alt. mode.

 

Runners up include:

 

2. Animated Cybertronian Deluxe Megatron - yeah, the alt. mode doesn't amount to much and he has the battle damage deco. He looks nice in bot mode though and is very poseable and oozes character.

3. G2 Hero Megatron - One of the better executions of a poseable tank Megatron.

4. Masterpiece Megatron - Nice looking, but honestly...I only got him to compliment my MP Prime. Basically a nice TF statue that happens to have a pain in the ass transformation.

5. Armada Megatron - Totally had the potential to be one of the best tank Megatrons ever if he hadn't been hindered by random orange plastic/highlights and completely avoidable poor leg articulation.

G1, and I guess MP can be a part of that, but the G1 toy's gun mode is a lot of fun. Classics is nice, but not as good as modern day gun-former could be.

Of the ones I have:

 

1- Cybertron Leader Megatron, 3 kick-ass modes and swivelling horns o' evil

2- Movie Leader- as someone said, I can't put my finger on it, but he's just mean-looking.

2- Energon (Leader?), cool jet mode WITH LANDING GEAR thank you Hasbro, and a nice G1 Galvatron homage bot mode

 

I don't have Masterpiece or Animated Leader, but they both appear to be insanely cool. Toss those into my list, and Animated would be #1. MP, jeez, gun-mode Megatrons just leave me cold, but that looks to be an amazing piece of engineering w/ a SOLID alt mode. Prob. #2.

 

Honorable mention to G2 tank Meg, I LOVE his cannon and its repeat-fire action!

As I don't have the Masterpiece or Animated Leader versions yet, I voted for Cyberton Megs. He's a triple changer, has decent gimicks, and he just looks sweet.

if galvatron repaints were included i'd say cybertron galvatron.... but since the purist in me say he's probably not a valid choice i'm gonna say mp megatron

Materpiece, followed closely by BW TM2 Dragon Megs followed closely by BW Megs