There are some designs that were only in the comics briefly, that I enjoyed quite a bit. These were usually versions of characters in alternate reality settings.
Age of Apocalypse: specifically Sunfire, but also Nightcrawler as he's just so natural with a sword--Though I didn't like the change in Nightcrawler's personality in the AoA version. Sunfire is just a dick like usual, but Nightcrawler lost all his charm.
Age of X: Along those lines, I like the look of Rogue here with her skull glove:
Gambit's ok, but he's basically Metal Gear Solid Gambit and Gambit's look has usually been pretty good regardless. While Rogue's look is cool there, I'm also a big fan of her modern green and white uniform and her classic 90's green and yellow with the leather jacket look. All the others, like Extreme X-Men and her early pre 90's day looks are shitty comparatively.
House of M: Iron Man's Gundam/Transformer look here was a fun change. Not one that I think would work consistently, but I liked the direction they went in and wouldn't mind seeing this being one of his special occasion armors.
Negative Zone Gladiator: This isn't an alternate reality version AFAIK but it fits with the theme. Johnny Storm as he was when he came back from the negative zone was a pretty nice redesign. It was the first time Torch came across with some kind of intimidation, which makes sense. The guy should be intimidating. He can set you on fire.
Side note: Whitey Spidey however, I'm less big on, although I liked the white suits just fine for the FF in general. And it's not that I hated Spidey wearing the team colors, but it was no black suit Spider-man, and doesn't hold a candle to the original.