Your claws are your fastest weapons. You can swipe about six times per second if you hold down the claw button, or if you tap it you'll get a quick double swipe. Claws are an average weapon to use against both Predators and Marines. If you run circles around your enemies constantly clawing them, you'll wear them down and deplete their ammo whilst hurting them. Also, your claws do double damage if the enemy is not facing you.
Tail (AvP & AvP2)
Your tail coils up like a snake when you hold the button down, and on release it strikes out. In AvP, if you just tap the button, you'll get a quick stab, while the charged tail attack does much more damage. Your tail will kill a Marine instantly if you hit them in the torso or head. It is less effective on Predators. In AvP2, the tail delivers a neurotoxin to the enemy's bloodstream while dealing damage. This neurotoxin will stun the enemy temporarily, making them woozy.
Secondary Jaws (AvP & AvP2)
This is the hardest weapon for you to use, but regardless of your enemy, it will kill them instantly. To use it, line your head up with the enemy's head until you see your jaws come into the screen. Then press the Claw button, and voila! This is a great weapon to use on someone when their back is turned to you. You will also regain some health when you do this, so try and bite dead enemies as well.
Pounce (AvP2) The Pounce attack launches you at the enemy with your claws outstretched. This attack not only does severe damage to the enemy, but also brings you within close range, where the Alien is most dangerous. However, using this attack will destroy the enemy's body, so you cannot gain health from the corpse.
Specialties
Pheromone Detection (AvP & AvP2)
Aliens can detect the pheromones of other creatures. This shows up as a bright halo around living creatures. You cannot detect pheromones if you are using your night vision. Humans have blue pheromones, Predators have green pheromones, and Aliens have red pheromones. Synthetics give off no pheromones.
Wall-Crawling (AvP & AvP2)
By holding the crouch button you can climb up walls and run along ceilings. This is good to reach far off places if you need to escape, plus to drop down on top of unsuspecting enemies. Be careful, as your sense of direction is easily lost. In AvP2, if you are not using your night vision, arrows will show you if you are crawling on the floor, walls, or ceiling.
Night Vision (AvP & AvP2)
This is the vision mode for the Alien. It allows you to see in pure darkness and only blurs your vision slightly. You can use it in well-lit areas as well. You cannot detect pheromones while using this vision mode, and in AvP2 you cannot see the directional arrows that help you while wall-crawling.
Accessories The Alien doesn't have any. However, you can destroy the accessories of Predators and Marines by clawing them.