I'm a big fan of heroes who take up the mantle of a another hero, be it temporarily or by really making the name their own. I don't intend this list to be all-inclusive, but I'd like to cast a pretty wide net, so suggestions are most welcome.
- brief glimpses of the future (e.g., Kal Kent),
- minor characters (e.g., Stan Silver Ray),
- most alternate worlds/elseworlds characters (e.g., Kingdom Come Superman, Carrie Kelly),
- villains (e.g., Harry Osborn Green Goblin, Axel Walker Trickster),
- characters whose origin includes a built-in legacy we only see in flashbacks (e.g., The Phantom),
- characters who are more related contemporaries than legacies (e.g., Miss Martian to Martian Manhunter, Power Girl to Supergirl),
- characters who are sidekicks but have their own mantle (e.g., Robin to Batman, Spider-Girl to Spider-Man),
- ripoff/homage characters (e.g., Rorschach to the Question, all the Superman knockoffs)
List is in no particular order, especially after the List update that means you can't organize lists over 100 at all.