I'd say Luke as we first saw him in ANH... as things go, the outfit is one of the most memorable and etched in everyone's minds. Also clearly shows his origins as a simple boy growing up on a farm with the dressed down look, before he changes to the more form fitting flightsuits etc.
Vader is the most iconic villain of all time. His name made people cower in fear let alone the sight of him. When you look at Vader he is the personification of the dark side and power. Whats not to love?
For me its the Sandtrooper, or as Lucas called them "Stormtroopers in combat order"
Stormtrooper armour + pouches + pauldrons + BFG's = awesome!
I've been a Sandtrooper with the 501st since 2001:
Obi-Wan Kenobi from A New Hope.
Not just because this was the classic design for the Jedi, but so much of the character is defined by this simple costume.
The Jedi were humble and simply dressed, function over form. But also you see that despite the darkest times the Jedi order had seen in such a long time he was still devoted to upholding and believing that the Jedi could recover from something like near destruction of their order. This very subtle thing to me showed that Kenobi never gave up on the Jedi despite have little to no hope that the order would survive. It's one of the many costumes that informs the character and universe it's in and I love it because it does this while keeping the costume so simple.
I am most fond of C-3P0. 3P0 and R2 always reminded me of Laurel & Hardy or Abbot & Costello.
Always raising a fuss and nothing is ever quite right. Always funny. Such a great character!
I have to go with AT AT Driver - Just looks bad ass!!
Got this image from - http://www.starwarshelmets.com/index.htm
Star Wars Helmets - Hope you don't mind me using this image - Love your site!
My favorite is also Han's ESB costume. I love the jacket, white shirt, and the contrasting brown pants/yellow stripe over the blue pants/red stripe. Aside from liking the combo over the ANH, it shows he dressed for the cooler climate ditching the vest for a long sleeve jacket. Yea it doesn't zip up like Luke's jacket but it doesn't have to cause he's Han freakin' Solo! He's got the best blaster, best ship, best co-pilot, and of course the best duds in the galaxy far, far away!
for me its the Luke Jedi outfit. With his cloak,he's mysterious as are the Jedi ,but his outfit is a visual example at the hint of his struggle with the dark side. That struggle is apparent near the end of ROTJ as well as in the books which take place after. same struggle we all face from time to time in life.
Not only was it my first non-Ben Cooper Halloween costume (shown here -- yep, that's a calculator for the control panel), I get a chill up my spine every time he makes his first appearance in the Rebel blockade runner.
I also felt his costume looked too "plastic-y" in the sequels. In the original movie, it looks much more metallic. I also prefer the tunic over the chest armor. That's just how I roll...