Alien. I love to stalk my prey in the darkness, hissing at them, watching them fire blindly. Then when they are isolated and the time is right, I strike.
Oh, by the way, sometimes when I play AvP2 as an Alien, I act like a Marine should. Anybody heard of a guy name Xeno-Warrior? That would be me. I set up a main base for Aliens, assign posts and strategic plans based on what area is controlled by who, then use series of ambush attacks from my fellow Aliens to wipe them out. The I quickly do a scan of the area while the Aliens retreat to the main base, or "Hive", so that while the marines look they cannot be found. I quickly establish different ways into the areas I am scoping, setting up new plans of attack based on where they position themselves and try and wait. Then, we wipe them out again using the newly developed routes, and then are able to travel throughout the map, efficiently killing off the enemies as they try to recover.