A classic: John Sayles' half eaten burger sitting next to a tray with brains on it in The Howling (one of a few great meat related gags in that movie)
also, there's another scene I've got memories of, but I just can't remember the damn movie. I'm thinking it's an 80s American horror movie (maybe horror comedy?). It's got a geeky looking morgue attendant with glasses, there's a fresh corpse on the slab in the middle of the room, and he's eating like a really messy pizza or something, and then he leaves the food on the table and the camera lingers on it for a bit just to get the grossness across. There might be other body parts around the room too.
Not much to go on I know, but someone help me out with this otherwise it's gonna bug the SHIT out of me.