Cabaji

Cabaji is the second mate in Buggy's crew as well as their primary swordsman who combines it with acrobatics (mostly on a unicycle) to fight his enemies. He fights with Roronoa Zoro no sooner than after being introduced and plays dirty by kicking Zoro's wounds whenever he has the chance. But once Cabaji is knocked off his unicycle, he is easily defeated by Zoro's 'Oni Giri' which cuts open his chest.

After Buggy's crew was defeated by Luffy, he fought with the 'other' first mate Mohji for the title for the next captain--both were knocked out by a sleepwalking Richie, who gained the title (though lost it just as quick). However, he returned to his former position when Buggy resurfaced.

During the Loguetown attack, Cabaji accompanied Buggy and Alvida to fight against the Straw Hats and Navy. However, despite wanting to have a rematch with Zoro, he didn't get a chance to do so.

(Source: Wikipedia)