Livia?
Richie?
Gloria's roast beef?
Ralph?
The Shah of Iran?
Gravity?
I gotta go with Ralph. He was such a unique character for me. What's great about this show is that he was only around throughout seasons 3 and 4, which are in the middle or lower tier for me. I think I like him so much because he goes against so many mob stereotypes.
"I hate to do it, Artie... but I think I'm gonna pass. Sorry. Because if you don't pay me back, I ain't gonna be able to hurt you."
"Tomorrow I can be on time, but you’ll be stupid forever."
Livia was the villain of this thing of ours. If she hadn’t been such a miserabe, Tony might’ve ended up selling patio furniture. Or at least he could have been a better boss. Instead he is just like her. He pits each member of the crew against the others and manipulates the fuck out of everyone.