The use of the word "epic" in the title could mean any of its uses, possibly "awesome," could be "larger than life," or it could mean "it's a long story" as it pertains to these Halloween costumes.
Chris Miller made his own Bender costume. The eyes moved by a servo controlled by his hands! He was a finalist in a costume contest, but I can't imagine what costume could beat this.
Dr. Octopus is the superbad villain from Spiderman. It's not a simple costume to pull off, but Rob at Cockeyed did it in 2004 and posted the complete story of building and using the contraption. He didn't win the costume contest, but no doubt enjoyed more internet fame than the winners.
Have you ever looked at a broken umbrella and thought about how it resembles a flailing bat? I have, since most of my umbrella break pretty quickly. Lenore at Evil Mad Scientist Laboratories made this Umbrella Bat costume out of one umbrella and a hoodie, and posted instructions so you can do the same.
This Trash Can costume is also a prank!
When I was a kid there was a guy in our neighborhood that used to jump out of the bushes in a gorilla suit and scare the bejeezus out of us. It was one of my fondest memories of halloween. Last year I decided to be that guy. Unfortunately, I don't have any bushes. An alternative would be to build a trash barrel disguise. I built the disguise below and then sat in it right on the front lawn. Not one single kid realized that It wasn't a trash can and I scared so many of them that I lost count.
You might not recognize the name Caterpillar Power Loader J-5000, but surely you remember the mechanical power suit Sigourney Weaver used to fight the alien queen in Aliens. Ben Hallert built this one for Halloween last year. Read his story with links to photos and a video. Hallert previously made an APU costume from The Matrix, and a Mech Warrior costume.
The Flaming Carrot is one of the more bizarre comic book characters you'll ever encounter, but it's the look that makes a great costume, rather than the backstory. RoG posted details on how he contructed this one.
Transformer costumes may be hot for this year, but Mark has been making and selling them for years. These costumes will actually transform into vehicles, but it may take a bit of practice on the wearer's part.
Jay Maynard, the Tron Guy, shows you step-by-step how he made the costume that made him an internet legend.
Honus at Instructables has already finished two Ghostbusters costumes for this year (and will possibly have a third). He also posted instructions for making your own, complete with goggles and weapons. The backpack really makes this; I hope it isn't as heavy as it looks!