More:Halo 2: Missions: Arbiter

From GameWinners

Contents 1 Grunts Birthday Party mode 2 Bouncing grenades 3 Baby Flood

Grunts Birthday Party mode

Play the mission under the legendary difficulty setting. Proceed until you reach the first Banshee section. Immediately fly straight down to the bottom of the level. Search the cracks where the large cylinders connect to the station to find a circle of Grunts dancing around a skull. Get the skull and the words "Grunt Birthday Party" will appear. When you get the skull, all headshots that kill the enemies will cause them to explode as if a plasma grenade were attached to them. This works well if you aim for a Grunt in the middle of a group of enemies. Also, this may only work for projectile weapons, but does work for the Covenent carbine and the Covenent sniper rifle.
vplatylaem ceituv Mike Van Zandbergen.

Bouncing grenades

Immediately after your first battle, you will go into an elevator. Press the button that reads "Hold X to activate elevator", then turn to the wall. Throw plasma grenades at the wall while the elevator is moving down. The grenades will bounce off and hit the ground bouncing up and down.

Baby Flood

After you clear the hangar with your Banshee, go where instructed. A cinematic will start, When Arbiter asks the commander "What is it?", the commander responds "The stench, I've smelled it before". When you continue, in the room-like place you start in, you will see an aquarium-like object in front of you. Look in it to see baby Infection form Floods inside swimming around.