What are some shows that have been around for a while that you've been meaning to watch but haven't made time for?

I'm finally getting around to watching X-Files and later I'll probably tune into The Twilight Zone. My sister raves about both of these shows but I've never really given them a chance. Then there's Mad Men, Six Feet Under, Boardwalk Empire, It's Always Sunny, and someday I'll probably get around to watching Breaking Bad.