More than 61,000 people attended Denver Comic Con earlier this month, and odds are that more than 130,000 will attend San Diego Comic Con next month. Hardcore fans like these are why Iron Man 3 is a billion-dollar box-office success and The Walking Dead ended as the top-rated TV show of the fall season. They're looking for edgier comics-sourced fare on the big screen.

Would family-friendly Walt Disney (DIS -0.10%) ever make an R-rated comic-book film? The opportunity is too big to pass up, says Fool contributor Tim Beyers in the following video.

Consider Time Warner's (TWX) success with Christopher Nolan's Batman series. The Dark Knight may very well be rated PG-13, but only the clinically unconscious would call it a kids' film. Heath Ledger's Joker is as dark a character as you'll find in a comic-book film, and that one earned a billion at the box office when doing so was a rarity. Overall, Nolan's Batman series earned Warner more than $2.4 billion in global box-office receipts.

Marvel, meanwhile, has plenty of characters that could star in a darker comic-book film. The Punisher is an obvious choice, Tim says, though Lions Gate's (LGF-A -1.18%) two tries with films based on the vigilante did poorly enough that the studio returned the movie rights to Disney.

Marvel should put the character to use soon. Or choose another. Hundreds of characters in the Marvel universe are violent enough to star in an R-rated film; Disney is leaving money on the table by sticking with lighter theater fare.

Interestingly, The House of Mouse isn't so prudish in other areas. Next week, Activision Blizzard releases to stores a particularly violent video game featuring the mutant assassin Deadpool. An R-rated comic book film would be no different, as well as an appreciated catalyst for investors expecting Disney to use all of Marvel's assets to boost profits.

Which characters would you choose if Disney were to greenlight an R-rated comic book film? Tim Beyers singles out two more besides The Punisher in the following video. Please watch, and then let us know which hard-boiled comic-book storyline you think would play best at the box office.