Now it's used mostly by Italian-Americans to mean 'trashy' Italians, the ones who didn't give up on their culture and become like white american people. Lately I've heard it directed at the Sopranos characters and the Guidos from Jersey Shore.
Me: Ma the guy I work for wears tons of gold chains and walks around like he doesn't care what other people think.
Mamma: What a gavone.
Me: Ma my friend Lorenzo invited me to his family cook-out.
Mamma: Oh gawd don't go they're a bunch of gavones.
Actions: Fills his plate a mile high. Stuffs his face. Devours the food. Doesn’t even taste the food prior to swallowing it down.
WASP #1: Who are those gavones eating all the clams?!
WASP #2: They must be from Staten Island.