Man, I think there are so many talented artists out there who passed far too early. For actors: Ledger and River Phoenix definitely top the list. I absolutely adored Stand By Me and My Own Private Idaho. And seeing Ledger in Brokeback Mountain and The Dark Knight made it clear the man had a real gift. Musicians: Lennon, Cobain, Jeff Buckley, Hendrix, and Elliot Smith (surprised not to see him up here already). Every single one of them were major contributors to their respective genres, and each helped shape it (Smith primarily influenced the indie scene for anyone not familiar with him). Writers: Douglas Adams, John Kennedy Toole (he wrote a Confederacy of Dunces, which wasn't published until after his suicide but is now considered a classic), and Edgar Allen Poe (he was only 40).