Clooney

"After several years, Dread Pirate Roberts was so rich he wanted to retire. Clooney was his friend and first mate, so he gave the ship to Clooney, who had an identical experience to yours: the first ship he attempted to board nearly blew him out of the water. So Roberts, realizing the name was the thing that inspired the necessary fear, sailed the Revenge to port, changed crews entirely, and Clooney told everyone he was the Dread Pirate Roberts, and who was to know he was not? - Felix Raymond Ryan." Clooney was a pirate in The Princess Bride.

The Princess Bride
Clooney originally served on the ship Revenge as the first mate of the Dread Pirate Roberts, who had been marauding the seas for five years.

When Roberts made it clear that he wanted to retire, he gave Clooney control of the ship; Clooney's first attempt at boarding an enemy ship went badly, so Roberts eventually passed the title onto Clooney, while serving as first mate under him. When the crew had adjusted to Clooney's leadership, Roberts retired to Patagonia.

Clooney eventually passed the title to Cummerbund and served as first mate under him before retiring.

Trivia

 * Unlike Cummerbund and Felix Raymond Ryan, Clooney is not mentioned by name in the 1987 film adaptation.