Alan Scott: Year One
(but that story would probably be titled Green Lantern: Year One, since thats who he was at the time.)
But I would LOVE to see that.
Lobo: Year One might not be so bad. It could show him in his original costume and original look, and he would be slightly depowered. It might be interesting.
Martian Manhunter: Year One would be really awesome. To see him come to earth, and decide to be a hero.
JSA: Year One would be cool. I'm a little confused about their origins anyway. I mean, weren't they originally the JLA from another reality or something?
Hawkman: Year One perhaps. Revisit him and Hawkgirl's first year on Earth.
I think I would like to see some old heroes in Year One. Like the original Flash's Jay Gerret, or Alan Scott,
also
Wonder Woman, Superman, the Hal Green Lantern, the second Flash,
the Spector: Year One. To see him die and his first year of being the spirit of justice and all that.
Something that might be really cool or at least interesting is a villian's Year One, like Joker: Year One or Lex Luther: Year One. Maybe Brainiac: Year One or someone along those lines.
To see their first year as an arch enemy through their own eyes, because no one thinks of themselves as a bad guy.
What bad guy would you LOVE to see a Year One for?
I'll think up some later.