Flood Friends

Summary
In Halo: Combat Evolved you were able to neutralize Flood forms and make them harmless. Called Flood 'Pets' or 'Buddies' these zombies would still try and follow you around and could then be used as shields, taking enemy fire while you crouch and shoot between their legs.

Walk Through
This can be done on any level with the Flood. It works particularly well with the Assault Rifle and Pistol, though I would reccomend the Plasma rifle or Plasma pistol seeing as they cause less damage. When you spot a Flood, shoot off its tentacled arm. On higher difficulties, you may also want to shoot off the elite infected flood's head, as this may be used as a weapon from time to time. If they are carrying a weapon, shoot off their right arm as well. Only the left arm must be amputated, and on Human infected flood, the head poses no threat. The arm in which they hold a weapon is only dangerous if they have a gun. After taking off the left arm, and sometimes the head, the Flood are incapable of hurting you. The number of Flood buddies you can make is technically indefinate, however the game will begin to lag after 6-7 flood buddies are acquired, and lags severely when more than a dozen are present.

Halo 2
Unfortunately in Halo 2 the game designers changed the Flood attributes. so that once you shoot the arms off a Combat Form it will shortly pop into an Infection Form. However, by shooting the left arm of a human flood that is not carrying a weapon, you can create a halo 2 flood buddy (though these tend to push you around, they cannot damage you).

Related Links

 * Flood
 * Combat Form