Deep in the bowels of the Black Mesa Federal Research Facility, a decommissioned missile base, a top secret project is underway. A portal has been opened to another dimension, and human science has never seen anything like the world on the other side.
You are Gordon Freeman, a young research associate in the Anomalous Materials Laboratory. You have limited security clearance and no real idea of just how dangerous your job has become, until the morning you are sent alone into the Test Chamber to analyze of a strange crystalline specimen. A routine analysis, they tell you. Until something goes wrong.
Is it sabotage? An accident? Or is it something you did? All you hear is screaming; all you see is spacetime shattering. The next thing you know, the entire Black Mesa Facility is a nightmare zone, with sirens wailing and scientists fleeing in terror from the things their co-workers have become.
Hordes of creatures from the far side of the portal are pouring through rifts in the local fabric of reality. Monsters are everywhere. Madness rules. You head for the surface, but the usual routes are impassable-closed off by the disaster, infested with headcrabs and houndeyes and increasingly larger and hungrier creatures.
As Gordon Freeman, you must enlist the help of traumatized scientists and trigger-happy security guards to get through high-security zones, sneaking and fighting your way through ruined missile silos and Cold War cafeterias, through darkened airducts and subterranean railways. When you finally come in sight of the surface, you realize that the inhuman monsters aren't your only enemies-for the government has sent in ruthless troops and stealthy assassins. Their orders seem to be that when it comes to the Black Mesa, nothing gets out alive... and especially not you.
When even your own species turns against you, maybe you'll be glad to see another portal beckoning. But then again, on Earth you have allies; while on the far side of the portal, nothing at all is familiar except the sense of danger.
Save the Earth? Well, maybe. But that's a pretty low priority compared to saving your own skin.
Taken from Half-Life's Site
Team Fortress Classic
Team Fortress 1.5 (TF) is Valve's new add-on for Half-Life that combines the thrilling first-person multiplayer gameplay of the original Team Fortress with Half-Life's leading edge technology. In Team Fortress 1.5, you play one of nine roles or classes, of which are listed below, and then join your teammates online or over a LAN to battle against enemy teams. Each class has unique weapons, items, abilities, and style of play.
Team Fortress 1.5 brings the social multiplayer gaming experience to new heights. The varying strengths and playing styles of each class and the different objectives for each map encourage you and your teammates to work together and add a level of strategy and interaction to TFC that you don't find in other first-person multiplayer action games.
Scouts are the best flag capturers, so they are utterly essential in any map which involves a flag (maps with objectives like Capture the Flag or Territorial Control). Scouts can be effective even without firing a single shot, since their strength lies in their speed rather than in their combat skills. If you like moving twice as fast as everyone else, and screaming for an escort as you escape the enemy base with the Flag and the entire enemy team pursuing you, then the Scout is your class.
The Sniper is the only class that can kill an enemy on the other side of the map with almost no warning at all. Be careful though, for if the enemy engages you at close range you're weaker than most of the other classes. If you like settling down into a good sniper position and methodically killing every enemy who exits his base with a single shot to the head, then the Sniper is for you.
The workhorse in any TF team, soldiers perform well at any task and specialize in none. If you like killing lots and lots of enemies in straight man-to-man combat, this is the class for you. Soldiers are a core class in any offensive or defensive squad.
Carrying more explosive weaponry than any other class, the Demoman clears whole rooms in seconds. He's essential on maps where the use of high explosives can destroy barriers, allowing access to more entrances into the enemy base. His remotely-detonable bombs make him a vicious defender in enclosed spaces. If you like watching the smoke clear and seeing bodies everywhere, the Demoman's your class.
A solid close-to-medium range fighter, the Medic moves swiftly and carries a gun that enables him to mow down any of the weaker classes without too much trouble. His real strength lies in his ability to heal himself and his teammates with his medikit. If you love seeing eternal gratitude in the eyes of your teammates, or can't aim at all and still want to be incredibly useful to your Team, go for the Medic class. You might not kill a lot of enemies, but the teammates whose lives you've saved sure will.
Heavy Weapons Guy
The name says it all. A slow moving, heavily armored beast toting an enormous assault cannon, the HW Guy can mow down any enemy in seconds. Not a lot of finesse in this one, since the cannon spits out so much fire you barely need to aim it. If you like picking a defensive position in a map and saying "No-one, and I mean no-one, is getting past here", then the HW Guy's the class you want.
A great first line of defense, the Pyro can easily knock chunks out of the enemy with his flamethrower. He doesn't have much in the way of killing weaponry, but he can make sure no-one gets into the base without being set on fire, and being burned alive tends to upset people. If you like running into a room, firing wildly, and then watching enemies run around screaming as they roast, then the Pyro is perfect for you.
A class who can disguise himself to look like anyone, the Spy can often walk into the enemy base, right past the defenders. Able to kill an enemy in a single hit with his knife, the Spy is someone you definitely don't want to turn your back on. After a few of their members have been knifed in the back, teams tend to get fairly paranoid. You know you're winning when they start to shoot each other for fear they're Spies. If you like matching your wits with the enemy instead of your reflexes, then the Spy is your class.
When your base needs some heavy defense, the Engineer comes to the rescue, building automatic sentry guns that track enemies and kill them. Able to repair his teammates' armor and build machines to dispense ammunition, the Engineer is often the core player in large defensive squads. If you need to defend your base against all those hardcore players out there with much better aim, the Engineer's the perfect class.
Taken from TFC Manual