Using your Physgun
The Physics Gun (most commonly known as The Physgun) is a tool/weapon that allows its user to manipulate almost everything in the game, with the exception of players and the map itself. It allows the user to lift, rotate the object in the air, place, and even freeze an object completely still, whether it's in midair or not.
Holding down your lmb left mouse button makes the Physgun emit a long blue beam from the front of the gun. Anything that touches the beam or vice versa will be grabbed by the gun and can then be manipulated, by you, into different positions.
rmb right clicking allows you to freeze the held object in place regardless of where it is.
Holding down e (your use key) allows you to rotate the object if grabbed by using the mouse. Your mmb mouse wheel, allows you to drag the grabbed target to them or pull it away, although the same thing can be done by holding e and walking forward or backward (w and s respectively).
The Physgun can also straighten out the angles of a prop. It is done by holding down ⇧ shift and e (your 'use' key) and moving the mouse around.
Reloading (r) with the physgun causes the bones of a highlighted rag doll (Highlight by rolling the crosshair over it) to unfreeze.
Reloading twice causes all props you've spawned (so far) to unfreeze. You may want to avoid doing this by accident.
The Physgun is a tool and has no capability as a weapon in itself. As such, it cannot be directly used as one, but rather must be used indirectly. Common means of doing so are grabbing large, heavy objects and whipping them around and into enemies. Other, more trap like methods are taking weighty props such as cars and containers and freezing them above enemies only to unfreeze and let the weight do the work, or holding back motorized or otherwise motion-constrained props until a time where releasing it will kill something.
As mentioned previously, the Physgun can almost grab anything regardless of it's weight. The few things that it cannot pick up are the objects built into the map by default, such as walls, windows and fences, and other players. Beware; sometimes players will suddenly lose control of the grabbed object if among other players, and if bumped or brushed up against, the object may instantly kill a player by accidental release and ricochetting. The best thing to do in this case is to make sure that there is enough space around you to manuver the object.
Posing ragdolls with the Physgun can be tricky. Once ready, the best method is to start with the head, then the torso, and lastly the limbs. One can also toggle on slow-movement-noclip by pressing ctrl, which will let them make very precise adjustments.