Daredevil - Wally Wood re-design

Captain America - Silver Age version

Vision - Original John Buscema design

To note:  There are many others that I think have great (usually simple designs) - Steve Ditko's original red & gold Iron Man armor, red & black Spider-Man and Green Goblin; Gil Kane's Adam Warlock, Green Lantern and Atom; Jack Kirby's blue and yellow Goliath, Fantastic Four, Black Panther, Black Bolt and Doctor Doom; Neal Adams' Angel and Green Arrow; Dave Cockrum's Nightcrawler and Thunderbird; John Romita's Punisher; Infantino's Deadman and Silver Age Flash; Don Heck's Sunfire.

It's really interesting to compare different character designs by the same artist - some of the, like Gil Kane and Dave Cockrum have a very distinct style when it comes to designing them.

Captain Britain (2nd costume - Alan Davis)

But, my absolute favourite...

Vindicator / Guardian

Wolverine classic

Deadman

Punisher original 

Batman's black and grey, in the form reintroduced to us in the 80's by Mazuchelli. 

The Angel--the blue and white by Neal Adams

Ms. Marvel--by Dave Cockrum

Galactus--by Jack Kirby

Spider-Man--by Steve Ditko

Adams, Cockrum, and Kirby are just head and shoulders above everybody in the design and redesign department, and Ditko did some all-time favorites.

I'm pretty sure he means black of course with blue highlights.

The Angel has had a few nice costumes (the red & gold version of Adams creation works well as does the X-Men school uniform), but he's had plenty of bad ones as well (like the suspenders look when they received their "graduation uniforms")