Right leg (Blue with rainbow highlights): Rainbow Dash
Left leg (Yellow with the blue butterfly knee cap): Fluttershy
Right arm (Orange with the large apple emblem): Applejack
Left arm (White with the drill): Rarity
Left torso and shoulder pad (Sun emblem): Princess Celestia
Right torso and shoulder pad (Moon emblem): Princess Luna
Belt, backpack, and shoulder cannons (Including the pink fluff behind the head): Pinkie Pie
Head: Twilight Sparkle

I'm both impressed and a little worried :lol

I just want to let you know that I decided against putting an explanation for why each character formed a specific body part and why they had whichever weapon. :p

Why? Go for it, I kinda wanna know.

Fluttershy and Rainbow dash form the legs because they are both Pegasi. This allows the mech to stand on clouds in addition to move much faster than normal (Since any wings would be in proportion to the individual body, not the combined form).

Applejack (Right arm) is famous for her leg strength and bucking tree (Using both her hind legs simultaneously in one powerful kick).
(The cannons are her legs)

Rarity has a drill because she's a Unicorn and unicorns have horns (Admittedly rather weak reasoning).

Twilight is the head by virtue of being the main character, and she's set in between day (Celestia) and night (Luna)
[Day - Twilight - Night]

Pinkie Pie is what holds it all together because she's the one that holds the group together as a whole.
She's also the shoulder cannons because she makes occasional use of a "Party cannon."

I once found a really bad-ass super robot anime style pony robot.

Too bad I can't find it. :(

This Mech is still a mess, but atleast now the mess makes a little more sense.

http://24.media.tumblr.com/1c4ff21a4...6rlwo1_500.png
http://25.media.tumblr.com/6f160e3c3...6rlwo2_500.jpg
http://24.media.tumblr.com/a36d68200...bqr6o1_500.jpg
http://25.media.tumblr.com/faf15fbae...iv92o1_500.jpg

Gosh...this thing is a mess...I mean, I love ponies, and I love robots...but I've seen better.

now count up your sins

http://i295.photobucket.com/albums/m...31364952_n.jpg