Michael Steele. I don't like him but he's the quintessential RINO.
In what world is the former chair of the RNC a RINO?
People change over time. Jimmy Carter is now seen as a progressive hero by many, despite his deregulation during the presidency. Al Gore has also moved to the left significantly post-2000.
I remember seeing his media appearances, with this hardline anti-Trump rhetoric and agreement with Democratic pundits, as coming off as being RINO-esque. He referred to himself as a "Lincoln conservative" on Bill Maher - I chuckled quite a bit there.