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.

Chunin 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
Later, 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 Raidou 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 during Furido and his gangs' attempt to invade Konoha and eliminate the Hokage. He is seen giving out orders to the chuunin troops.

Pain's Invasion arc
Here, he is seen with Yamato and several other Jonin helping to restore the village after Pain and Naruto's fight.

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.