What the game never tells you — Wiki

The rules that surprise people: from the minimap giving you away to what a plant survives.

Every point here comes from the game's own code and data. Each links to the page with the details.

Every shot you fire puts you on every enemy's minimap, as a red dot, from any distance. See Sound and the minimap.
Fully aimed and standing on the ground, moving costs you no accuracy. From the hip, it does. See Health and movement.
A fully aimed shot goes exactly where you aim if you fired your last one a second or more before. See Weapons.
After a sprint you can't fire for 0.3 seconds.
Getting shot kicks your aim. Holding a Kar 98k doubles it, and a Springfield or a Kar 98k Sniper makes it 2.5 times as big. Hits don't add up: only the biggest counts.
The gun kicking and swaying on your screen is only its model. Your aim doesn't move with it.
A bullet goes through one wall at most. A second surface stops it. See Wallbangs and collaterals.
A bullet only goes on through a player it kills, at full damage, through up to five players. Only the Kar 98k, the Kar 98k Sniper, the M1 Garand and the Springfield do it.

Crouched, prone or aiming down sights, you make no footsteps. Walking forward while leaning is silent too.
Jumping and landing always make a sound.
A second jump within 2 seconds is lower: about 59% of the height.
Jumping while crouched stands you up instead.
Gravity is twice the Earth's. A jump lifts your feet only 1.09 m, and a drop of 6.1 m already hurts. See Health and movement.
Strafing in the air can make you faster than running, as in Quake: nothing caps the speed your keys build in the air. You slow down again once you land.
Leaning against a wall leans you less, or not at all.

Grenades fly through most of the maps' invisible walls: the ones that only stop players. They bounce off the rest. See Grenades.
Running forward throws a grenade further, and the throw always goes 4° above your crosshair.
A grenade keeps 40% of its speed at each bounce, so it never rolls far.
A smoke thrown upwards covers a tilted box: the area it greys out turns with the angle you threw it at.

Walls don't protect you from the explosion. See Rounds and the bomb.
Getting shot doesn't stop a plant or a defuse. Only dying, or letting go, does.
Let go and you start again from zero. Progress is never kept.
Nobody sees how far along an enemy's plant or defuse is.
After the plant, killing the last attacker doesn't win the round. The defenders still have to defuse.

Every gun you buy respawns you on the same spot, with your new loadout. See Economy.
There's no selling. A new primary replaces your old one, which is gone.
The last round before halftime pays nothing: no round-win tokens and no loss bonus.
Survive and you keep your guns and unthrown grenades. Die and you start the next round with the free SMG.
Donate gives one token a click.

Any damage can earn an assist. The assist goes to the player, other than the killer, who did the most damage. Once the victim's health has come back, the earlier damage doesn't count. See How a match works.
Drop out and rejoin within 5 minutes to get your score and your tokens back.
Each team gets one tactical and one technical timeout a half. Every vote needs a yes from the whole team.
When you're dead you can only watch your own team.