Camping
The word is uttered with disdain and contempt, but "camping" is, when used properly, a legitimate and effective strategy. According to those who crucify me for doing it, "camping" is the practice of either a) holing up in an easily-defended, rather obscure location and getting the jump on the enemy by popping them out of nowhere or b) moving quietly across the map, hearing an approaching enemy, hiding, and then ambushing him. There is nothing inherently wrong with either.
Remember that, unlike death match games such as Quake, Counterstrike is a team-based game played within an attack-and-defend scenario or variation thereof. In the "hostage rescue" scenarios, for example, the Terrorists are on the defensive, attempting to hold off the attacking Counter-Terrorists. Likewise, in the "defusion" maps, the CTs defend their turf from the bomb-toting Ts. In either case, one side is occupying an area with the intention of keeping the other side out. Concealing yourself in a static position that offers you good visibility as well as the element of surprise is a sensible way to defend. Real combatants call this "digging in." Frustrated CS players call it "camping."
Granted, an attacker who "digs in" accomplishes almost nothing. Counterterrorists who camp in a "hostage rescue" map, for example, are nothing more than counter-productive unless the Terrorists venture outside in search of their enemy. (This isnt likely to happen, though, since as of B6 the Ts will win the match if they still have their hostages when the time runs out; they may as well wait it out inside until the entire team can afford heavy weapons.) But a defender who controls access to his enemys objective is simply doing his job.
A Case in Point: When youre the last Terrorist left in Canyon Siege because all of your teammates have dispersed individually across the map (and been taken out one-by-one by a cohesive CT team), youd be amazed at how many attackers you can waste by hiding out in the vent room. Position yourself in the corner by the door, facing the vent. Listen for someone climbing up to the vent opening. When a CT crawls through the opening, the first body part you see is his head an instant kill. Also, listen for attackers approaching the door and either fire through the door or whack em as soon as they slide it open. When all is said and done, you have single-handedly held off the CTs, kept your hostages, and won the match.
(Conversely, CTs should toss several grenades through the vent before entering in order to clear nasty buggers like me out of that room. Dont expect the hostages to survive, though.)
As I mentioned earlier, the other form of "camping" involves moving stealthily across the map towards your objective and taking every opportunity to ambush enemy players along the way. It is amazing that as effective as sneaking is (holding SHIFT while moving), almost no one does it. Ive made many kills by sneaking. In the Militia map, for example, Ive racked up several kills by sneaking through the sewer; when I hear an enemy running from the other direction, I move up to the corner around which he is about to appear and wait; more often than not, I am able to take him totally by surprise, kill him, and continue towards the enemy base. What also works is sneaking up to the corner and then around it; most players expect me to be running and so are unprepared when I appear and cap 'em.
Despite it's effectiveness (or perhaps because of it) I am constantly berated for "camping" as soon as I start racking up the kills. Anti-campers whine that capping someone while camping is "cheap." Maybe, maybe not. All I can say is that a "cheap" kill is still a kill, regardless.
I play CS within the limits set out by the game designers. Which means that I dont use head-shot scripts or cheat in any other conceivable way. Until those very same game designers implement some kind of "idle timeout" script to kill players who remain stationary for too long, I will continue to "camp." Because it is a legitimate, effective strategy that works.