Ragdoll

From GMod Wiki

A ragdoll is a posable physics prop that uses Valve's Source physics engine. A ragdoll can be posed in various forms by the player, using various props and physics objects to affect the ragdoll's pose. Radolls are produced by most killed NPCs and can also be spawned through the Q menu.

Posing a ragdoll can be quite tricky. One should always adjust the torso first, then proceed to the head, arms, legs, ect.

Some non-body ragdolls exist, such as the standard HL2 mattress.