Here's mine:

The Hal Jordan Green Lanttern-a great, simple Gil Kane design

Red & blue Captain Mar-vell-another Gil Kane design I think

Colossus-from JB's era

Superman-of course

Batman-without the oval, although I do like the variation JB did in Generations with the white oval.

Spider-Man:the original is the best but I do like the black costume also.

Iron Man-late 70's Romita/Layton version

Thor-the classic version but I also like the new chainmail look.

Although I'm not big on the characters themselves, I own a number of Iron Man and Green Lantern toys because of the their visuals. (Not that I dislike them either, mind you...)

The Ed Hannigan-designed robot Brainiac is a favorite of mine, as are...
Aquaman
Beta Ray Bill
Cyclops (Both Cockrum & Byrne's)
Deadman (Infantino, Adams)
Daredevil (Wood)
Doctor Doom (Both Kirby and Wood's)
The Falcon (Romita)
Hellcat
The Human Torch
The Impossible Man
Jay Garrick
Jor-El & Lara (Boring, Swan, & the Toth Super Friends designs)
Kid Flash (Yellow & Red)
Lightning Lad, Shadow Lass, Saturn Girl, Projectra, Brainiac Five, Wildfire (all Cockrum/Grell)
The Metal Men
Metamorpho
Mon-El (Swan)
Nightcrawler
Nighthawk (Romita)
Nightwing & Flamebird (Swan)
Nova
The Phantom Stranger (Aparo)
Plastic Man
Robotman (Both the original and the Staton Byrne-influenced design)
Rogue (Bomber Jacket version, despite the bad trend it set)
Rom. Spaceknight
The Silver Surfer
Space Ghost
Storm
The Thing (especially the Byrne era)
The Valkyrie (Both the Buscema version and the later white costume)
Wildcat

I find myself gravitating heavily these days to the Black Costume Spidey (not that there's a thing wrong with the original Ditko costume, or the slightly simpler Romita version.)

A recent renovation that I was surprising to find as appealing as I did was the Oliver Copiel Legion, especially the revised Wildfire.

Guilty pleasures: Wonder Woman (especially the Golden Age variety) and characters whose look is a "take" on an existing character's, such as Bizarro, Professor Zoom, or Web-Man (a one-shot Spidey Super Stories "clone" of Spider-Man.)

Hey, while on the subject of The Thing... I've had a question for the longest time and this is probably the best place I'll find an answer.  Most of my first contact with comic characters were as cartoons in my youth.  I discovered comics later on and mistakenly believed that the comics were based on the cartoons! 

Anyway, the F4 cartoon from my tender years featured Ben Grimm's magical ring to change himself to the Thing ("Ring, ring do your thing!").  I have never once found a reference to that in the comics.  Where did that device come from?

My Dream Marie Severin commission: the Thing-Ring Benjy Grimm incarnation of the Thing racing toward the viewer alongside Severin's Teen Hulk from Crazy Magazine.