Mr. 9

Mr. 9 was Miss Wednesday's assigned male partner during her infiltration of Baroque Works. Not much is known about him other than that he dressed like a prince and fought with acrobatic skill coupled with steel bats.

History
He and Vivi (known as Miss Wednesday at the time) meet the Straw Hat Pirates during the Laboon arc while trying to kill the whale to be used as food for their bounty hunting partners at Whiskey Peak. The Straw Hats gave them a ride later after they accidentally lost their Log Pose.

After Vivi was exposed by Mr. 5 and Miss Valentine, Mr. 9 tried to hold them off to allow her to escape as he had grown fond of Vivi during their time together, declaring that they were still partners (effectively placing their loyalty to one another before loyalty to the company, an act frowned upon by Mr. 5). Unfortunately, Mr. 5 (supposedly) kills him by hitting him with a Nose Fancy Cannon attack that exploded and knocked Mr. 9 into a river.

Trivia

 * In a recent character poll, Mr. 9 is currently ranked the 42nd most popular character in One Piece.