I just thought I would start this thread and see if I get any responses. I think a lot can be done with the character (and a lot has been done with him). Here are a few that I've either read or been thinking about reading.
Emperor Joker--the one where the Joker is granted the power of a demigod and uses it to repeatedly kill Batman. I don't really understand the whole part about turning the Chinese into Chinese food, though, probably culturally insensitive for today's audience.
Batman and Robin must Die--the Joker disguises himself as a famous writer to help the Bat family solve a really strange mystery. Batman, of course, shows up at the end, and everyone lives happily ever after, except for the actor pretending to be Thomas Wayne.
Batman Europa--Batman and Joker are dying from some deadly disease and have to team up to figure out what's going on. We discover that, among other things, the Joker speaks fluent French.
Slay ride--the Joker kidnaps one of the robins and takes him for a terrifying "joy ride" in Gotham.
The Elseworld stories with Jokester, Owlman, and Talon--the Jokester is upset to find out his daughter is dating Talon, Owlman's sidekick, and among other things, stages a roast for him at his comedy club. (Really, I think they should bring back the Jokester, not that Jester character unless they want to make them two different characters, and allow him to have a long run of stories. I mean, he's the Joker only without the violence and criminal mischief. It could totally work. We don't just like the Joker because he's violent; we like him because he's really intelligent, spontaneous, and just plain crazy--like the time he tried to get a copyright for poisoned fish! Jokester, though, is even funny, because his jokes rely on actual humor and don't usually involve killing people. I imagine the tamer and more playful Joker versions, like the one found in Batman the Brave and the Bold, would work for the Jokester. Hey, who can fans mention their ideas to at DC to get this to happen?)