Anything to add, just post and I'll throw it in the list.
~ DT = DOUBLE-TAP
~ NUMPAD refers to a key on the number pad located to the right of your keyboard.
~ [#] See tips regarding this particular keybind.
- - RUN/WALK: SHIFT (DT toggle)
- SPRINT: DT W
- PRONE: Z
- CROUCH: X
- STAND: C
- VAULT (step over fences): V
- LEAN (roll when prone): Q and E (Left and Right, DT toggle)
- CLIMB LADDER/ACTION: MOUSE WHEEL SCROLL / CLICK (often times you may have to re-position yourself to successfully climb a ladder, look for a up/down arrow) 
- - THIRD PERSON: NUMPAD ENTER (ensure you are in a 3rd person enabled server for this to work)
- ZOOM OUT/WIDER FIELD OF VIEW: DT NUMPAD -
- ZOOM IN: HOLD RCLICK
- IRONSIGHTS: TAP RCLICK
- HOLD BREATH: HOLD RCLICK (whilst aiming down sights)
- FREE LOOK: ALT (DT toggle)
- - CYCLE CHAT CHANNEL: , and .
- CHAT: /
- VOIP/PTT: CAPS LOCK (DT toggle)
- MUTE PLAYER: P > SELECT PLAYER > MUTE (located to the right)
- - BINOCULARS: B
- WATCH: O (DT toggle)
- COMPASS: K (DT toggle)
- NVG: N (DT toggle?)
- MAP: M 
- - OPEN INVENTORY: G
- PICK-UP ITEM: G or MOUSE WHEEL SCROLL / CLICK
- USE/CONSUME ITEM: RCLICK ITEM ICON IN INVENTORY (specifically the icon, rather than the name in the list)
- CYCLE WEAPON (cycle through grenades, flares, throwable items): F
- SWITCH WEAPON (cycle between your primary and secondary weapon): ;
- LOWER/RAISE PRIMARY (does not work with pistols): DT LCTRL or RCTRL + R
- ZERO (adjust distance of sniper scope/shots): PAGE UP / PAGE DOWN
- - FLASHLIGHT/HEADLIGHTS: L
- SIT: '
- SALUTE: \
- TOGGLE WINDOWED/FULLSCREEN: ALT+ENTER (I believe you have to press ESC to bring up the menu, then ALT+ENTER)
- - FLUSHING: If you experience graphical glitches, sometimes 'flushing' might help. To do this, hold SHIFT and NUMPAD - and type 'flush'.
-  CAN'T PICK UP AN ITEM?: I have occasionally struggled to pick up an item from a certain stash on the ground, usually because it is right next to a door. People often miss this simple tip: scroll the mouse wheel up/down until you have the option of 'Take x y z' or 'Gear'.
-  LOST? One of the best maps I have found online so far is AvidBlur's.