Most people have found a lot of skulls in halo 2 so I have wrote down the effects of some skulls I know about:
Legendary, armory, thunderstorm makes all covenant silver rank making legendary mode even harder.
Any difficulty, outskirts, blind skull disables HUD.
Legendary, metropolis, catch skull makes allies throw a lot of plasma grenades.
Legendary, the arbiter, grunt birthday party skull makes all covenant explode when they are killed by head shots.
Legendary, oracle, famine skull means weapons only have half ammo.
Legendary, delta halo, envy skull gives masterchief a cloak instead of flashlight and if you go through a checkpoint while cloaked and save then turn your xbox off and on again you will find yourself with and infinite cloak.
Legendary, regret, assassins skull makes all enemies cloaked even hunters jackals drones and brutes.
Legendary, qaurantine zone, sputnik skull makes explosions and melee have a better effect.
Legendary, gravemind, anger skull.....i think this means the brutes are stronger when they go berserk.
Legendary, high charity, iron skull means allies are immune to melee attacks.
Legendary, the great journey, black eye skull (i think) this means your sheild only recharges by melee attacking enemies and you can get your sheild way up to over sheild!
Added by: peter1234 Sep 17th 2005, ID#4583