1. Someone who, when playing xBox or Playstation on a the same TV against each other, looks at the other player's half of the screen to get an unfair advantage against the other player- Knowledge of where the other player is located and weapons they may have.
Usually in a first person shooter ex: Halo.
"Dude! How did you know know where I was? I had camo and the radar jammer... You're such a rubbernecker!!"
Slang: Someone who enjoys the act of slowing their vehicle to like 15 miles an hour on a motorway just so they can gawk at the wreckage of a van on its roof or a car on fire.
These people are a severe pain in the arse to emergency services, and they often cause tailbacks up to several miles.
I got held up on the M25 last night going home cause of some rubbernecker staring at a crash.