Tactical Shooter

If you've been living on Earth in the past few years, you've probably at least heard the term "First-Person Shooter". This refers to all those games where all you see is the gun in your hand and the enemies coming to collect your bullets. The 2000's have seen the production of countless games belonging to this genre.

However, for all their bang, First-Person Shooters seldom portray the actual experience of being in battle faithfully. Whether it be Bottomless Magazines, Hit Points or One-Man Army, they tend to stick to the Rule of Fun or at least the Rule of Cool.

Naturally, some game developers use the recent advances in videogame technology to produce games that try to stay closer to reality. In these games, surviving a battle takes less of a steady hand and lightning-quick reflexes, and more of the ability to plan ahead, use stealthy or underhanded means, and command several combatants simultaneously. Games that aspire to this goal are generally known as Tactical Shooters.

In order to "distinguish" itself as a Tactical Shooter, rather than a "mundane" First-Person Shooter, the game needs to conform to at least one of the following rules (and preferably, all of them):

Realistic Magazines: Each magazine carries a certain number of bullets. If you exchange magazines during the mission, you either end up with a half-empty magazine lurking in your inventory, or have to throw away the bullets you didn't fire. It is sometimes even impossible to pick up any extra ammo during the mission, even if enemies carry the same kind of ammo, although this usually irritates players regardless. If it's possible to refill half-empty magazines from other magazines, expect it to take more than a few seconds.
Realistic Bullet Damage: Bullets will kill you instantly, or at least hurt you badly. The idea is to avoid getting shot at all costs, meaning that you need to fire first and always keep the advantage.
Squad Controls: One of the most defining aspects of this genre. You rarely if ever work alone. Instead you are accompanied by several teammates, who require at least some degree of ordering about to do any good. Simply having them around does not fulfil this trope - you need to HAVE to issue them orders and count on their ability to perform those orders well enough. The game must be extremely difficult to complete without mastering this skill.
Subsystem Damage: Being shot in the leg, for instance, should mean you can only move at a snail's pace, and/or be barred from performing certain actions. Being shot in the arm or shoulder should at least incur penalties to shooting accuracy, if not prevent any manual actions completely!
Cover Mechanics: Hiding behind a solid object will increase your potential of survival remarkably (especially considering that being caught in the open will invariably get you killed). It may or may not be possible that special hotkeys or interface features allow you to peek out from behind the object, minimizing exposure.
Situational Awareness Aids: Some sort of interface is included to allow you to get a better idea of where enemies are coming from and/or the best ways to assault them. Sometimes this is a zoom-out of the combat area, but most often it's a minimal map with sketchy details on it. Expect the game to keep running while you're looking at the map!
Mission Planning: The possibility to examine a blueprint of the battlefield before embarking on the mission. May also include the possibility to give some standing orders, or even a meticulously detailed battleplan to your troops beforehand. Expect all plans to fall apart once combat starts - this is, in fact, realism incarnate.
Reduced Acrobatics The Jump Physics of a game is very limited in Tactical shooters, while your soldier may be able to get a hop or two, he does not have the agility of a rabbit. Also, running can be limited by stamina counter. That makes finding cover even more important.

Different games naturally feature different combinations of the above.

Also expect Nintendo Hard, especially if you've bought the game thinking it was just another cool FPS. These games take a lot of hard work to complete. Heck, some may take hours just to learn how to play properly.

Do note that some of the more modern First-Person Shooters may look deceptively like Tactical Shooters, especially due to the level of realism put into the physics engine and graphics. However, the distinguishing traits are all related to how the game is played, not how realistic it looks.

Compare Tactical Turn Based for games that try to achieve similar goals without a real-time, first-person experience.

Examples of Tactical Shooter include:

Rainbow Six is probably the Trope Maker. Later games move away from this.
Ghost Recon. Ditto.
Brothers in Arms is a light Tactical Shooter, featuring many of the above criteria while maintaining a general Rule of Fun atmosphere. That is, until you ramp up the difficulty to "Realistic"...
Full Spectrum Warrior takes this to the next level, featuring tactics on a Company level, not to mention an entire simulated war raging around you.
Operation Flashpoint and its sequels, Arm A and Arm A II.
The Police Quest: S.W.A.T series, except the second title which was not a shooter at all.
Damage Incorporated, a very early example based on the Marathon 2 engine.
SOCOM: U.S. Navy SEALs. Its latest reboot is more Gears of War.
SEAL team, from the early 90's - which was also one of the first shooters to feature polygon 3D graphics.
The STALKER series places the genre into a bizarre science fiction alternate history. Even bullet drop and travel time have to be accounted for. Even in super advanced body armor a group of enemies is a brutally difficult fight where one bullet to the head can drop you.
Counter-Strike (Half-Life mod)
Day of Defeat (Half-Life mod). It has bipods (mostly on machineguns) deployable on sandbags or floor, and not only integrated team communication via both voice (on two languages) and Hand Signals (with model animations support), but Sturmbots use those.
Smokin' Guns (Quake 3 mod), though without team features (it only uses fine-tuning of the stupid generic Q3 bot, anyway).