I'm going with Richie from The Dick Van Dyke Show. That little shit was BEYOND annoying. He screamed his lines constantly, and was pretty much an afterthought, as far as the scripts were concerned (sort of like the slightly less annoying youngest 2 kids on The Partridge Family). Who's your pick? Bonus: most annoying kid EVER in a major motion picture had to be the kid from The Poseidon Adventure. I was a kid myself in the 70s when that movie came out, and I wanted to punch that kid in the mouth for being so goddam annoying!