The announcer

The Announcer (voice by Jeff Steitzer) is the male voice in Halo: Combat Evolved, Halo 2, Halo 3, Halo 3: ODST, and Halo: Reach multiplayer that calls out certain phrases when the criteria are met (like the Announcer calling out medal titles when certain medals are obtained and general events in the game).

Achievements
Multi-Kill Achievements
 * Double Kill
 * Triple Kill
 * Killtacular

Spree Medals
 * Killing Spree
 * Running Riot

Events

 * "Game Over!"
 * "[Time left until a player wins King of the Hill] to win!"

Medals
Multi-Kill Medals
 * Double Kill
 * Triple Kill
 * Killtacular
 * Kill Frenzy
 * Killtrocity
 * Killimanjaro

Spree Medals
 * Killing Spree
 * Running Riot
 * Rampage
 * Berserker
 * Overkill
 * Untouchable

Events

 * "Gained the Lead!"
 * "Lost the Lead!"
 * "Tied the Leader!"
 * "Game Over!"

Medals
Multi-Kill Medals
 * Double Kill
 * Triple Kill
 * Overkill
 * Killtacular
 * Killtrocity
 * Killimanjaro
 * Killtastrophe
 * Killapocalypse
 * Killionaire

Spree Medals
 * Killing Spree
 * Killing Frenzy
 * Running Riot
 * Rampage
 * Untouchable
 * Invincible

Weapon Spree Medals
 * Shotgun Spree
 * Open Season
 * Sword Spree
 * Slice 'N Dice
 * Sniper Spree
 * Sharpshooter
 * Splatter Spree
 * Vehicular Manslaughter

Objective Spree Medals
 * Hail to the King
 * Infection Spree
 * Mmmm Brains
 * Zombie Killing Spree
 * Hell's Janitor
 * Juggernaut Spree
 * Unstoppable

Other Medals
 * Perfection
 * Extermination
 * Killjoy
 * Last Man Standing

Events
General Gameplay
 * "Defense!"
 * "Offense!"
 * "Betrayal!"
 * "Betrayed!"
 * "Suicide!"
 * "Sudden Death!"
 * "Round over!"
 * "Game over!"
 * "Gained the Lead!" 

Time Remaining
 * "30 minutes remaining!"
 * "15 minutes remaining!"
 * "5 minutes remaining!"
 * "1 minute remaining!"
 * "30 seconds remaining!"
 * "10 seconds remaining!"

Slayer/Team Slayer
 * "Slayer!"

Capture The Flag
 * "Capture The Flag!"
 * "Flag Taken!"
 * "Flag Stolen!"
 * "Flag Dropped!"
 * "Flag Reset!"
 * "Flag Recovered!"
 * "Flag Captured!"

Assault
 * "Assault!"
 * "Bomb Taken!"
 * "Bomb Dropped!"
 * "Bomb Armed!"
 * "Bomb Disarmed!"
 * "Bomb Detonated!"
 * "Bomb Reset!"

Oddball
 * "Oddball!"
 * "Play Ball!"
 * "Ball Taken!"
 * "Ball Dropped!"
 * "Ball Reset!"

VIP
 * "VIP!"
 * "New VIP!"
 * "VIP Killed!"
 * "Destination Moved!"

Juggernaut
 * "Juggernaut!"
 * "New Juggernaut!"
 * "Destination Moved!"

Infection
 * "Infection!"
 * "New Zombie!"
 * "Infected!"
 * "Last Man Standing"

King of the Hill
 * "King of the Hill!"
 * "Hill Controlled!"
 * "Hill Contested!"
 * "Hill Moved!"
 * Hail The King!"'

Territories
 * "Territories!"
 * "Territory Captured!"
 * "Territory Lost!"
 * "Territory Contested!"

Halo Wars
In Halo Wars, a multiplayer announcer is also present, however is not voiced by Jeff Steitzer. This announcer will announce the completion of every building and upgrade in the game. He will also alert the player of enemy engagements off-screen.

Halo Reach

 * "Killing Spree"
 * "Killing Frenzy"
 * "Running Riot"
 * "Rampage"
 * "Untouchable"
 * "Invincible"
 * "Inconceivable"
 * "Unfrigginbelievable"