Genma Shiranui

becomes the proctor during final rounds of the Chunin Exams after the death of Hayate Gekko. He usually has a senbon in his mouth.

Chuunin Exams arc
After Hayate's death, Genma referees the final round matches of the Chunin Exams. He battles Baki during Orochimaru's attempted invasion of Konoha. However, their fight is interrupted when Orochimaru calls off the invasion.

Search for Tsunade arc
In the anime, he and Aoba are assigned to announce Tsunade's inauguration as the Fifth Hokage.

Sasuke Retrieval arc
Genma is returning to the village from a mission with Raido Namiashi, Iwashi Tatami and Shizune, when he and Raido encounter the Sound Four. In order to defeat Raido and Genma, the Sound Four activate level two of their cursed seals, leaving Genma gravely injured and in serious need of medical attention. In addition to this, Genma and Raido barely had any chakra left.

Fire Temple Arc
Genma appears in this arc giving out orders to the chuunin troops during the Furido and his gang's attempt to invade the village and eliminate the Hokage.

Pain's Invasion Arc
Genma appears with Yamato and other Jonin helping to restore the village after Naruto and Pain's enormous clash.

Abilities
Despite the handful of fights he has been in, Genma has yet to be seen in combat. He can spit the senbon from his mouth as a projectile, although its usefulness is unclear. Given that the Sound Four needed to activate their cursed seals in order to defeat him, it is likely that he is a formidable fighter.

Trivia

 * Genma said during the Chunin Exams that Naruto has a 'mean left hook'. But during that time, Naruto did an uppercut, not a left hook.