From Halopedia, the Halo wiki
Jeff Steitzer is an actor and voice artist, best known for his roles in The Fugitive, Law & Order, and Alien vs. Predator 2.
Jeff plays the multiplayer announcer for Halo: Combat Evolved, Halo 2, Halo 3, Halo 3: ODST, Halo: Reach, Halo 4, Halo 2: Anniversary, and Halo 5: Guardians. He can be heard during matches announcing everything from "Double Kill!" to "Flag Stolen!" to "Game Over".