A superb Half-Life mod of shooting, aliens and entertaining gameplay combining both FPS and RTS in one multiplayer game.
The Frontiersmen (the humans) have some pretty neat weapons and abilities from default class to special class such as heavily armored and jetpack. The weapons are pretty cool and the utilities such as welder, shotgun, grenade launcher, HMG (Heavy Machine Gun), mine and grenade. Sometimes you get into actual fear in the game as if the monsters are watching you and you fall into their death trap unless if you look around and make sure.
The Khaara (the aliens) are pretty awesome and have much better abilities then humans (except their weapons can't be changeable and don't have a commander but they have gorges). Their's 5 classes of the Khaara; The Skulk is a small and fast killer, the Gorge is a builder that can spit web and acid, the Lerk is a flying class that can fly and attack with acid and claws, the Fade is a big humanoid creature that's incredibly fast and it can come from [i]anywhere[/i] and finally the Onus is a big and powerful monster that acts like a rhino but devour it's victims whole (though I was luckily never eaten). Though you can't select, as your default class is basically the Skulk, but you can evolve through a gestation egg for your abilities and classes.
Natural selection is fun and a superb Half-Life mod of shooting, aliens and entertaining gameplay combining both FPS and RTS in one multiplayer game.