A Spartan Utilizing Active Camo, a form of Invisibility
Invisibility is an abilty which allows the user to be unseen by anyone in the area. It works by bending light so it will not reflect off the user, rendering them unseen. This allows the user to be completely invisble and is extremely good for reconnaissance missions where the main objective is to obtain intelligence without alerting the enemy. However, a small shimmer is present around the figure of the person which can be seen if the onlooker is perceptive enough. If killing is not the main objective, Invisibility is great to weave through the foes.
There are one or two drawbacks to this method. One of them is that it doesnt disguise your muzzle flash from your guns, so most soldiers will have to resort to melee kills etc. Invisibility doesnt fool everyone and it drains power from suits of armour quite quickly so it can not be used for long periods of time.
The few races that have maanaged to perfect Invisibility technology are: