On the whole, I've found that bad, or at least flawed, fiction is the ideal source.
Oh yeah. If I ever do manage to write that fantasy novel I have (copious) notes for, it'll owe its existence to a TV show with a brilliant premise that was utterly, utterly wasted.

Good stories I just want to roll around in. Flawed stories I want to rewrite. (Which is why I'm a horrible person to watch movies/TV with. I either leave or talk through the whole thing.)