Even more so than in films or on TV, the medium of graphic novels is filled with a cast of supporting characters that rival the main protagonists and antagonists in terms of how important their actions and characterisation are. DC and Marvel, in particular, have an array of supporting cast members who've grown so popular that they've gained their own offshoot story arcs and even comics of their own. I've tried to largely stick to one or two supporting characters maximum per title in the interests of diversity, as you could easily fill a top 10 list with Batman, Spider-Man or Sin City characters. The list is in no particular order, though I have saved until last the character that I think embodies the function of a supporting character in the best way: intertwined with the story of the main protagonist, a crucial character that has been there ever since the start, but one that you could feasibly see carrying a successful title of his own. I also haven't included such famous sidekicks as Alfred Pennyworth, or any of the array of Thor characters currently appearing on the big screen. If I've missed anybody obvious, or you disagree with any of the choices on the list, let us know in the comments section below...