Contractors often receive calls to fix holes punched in sheetrock, or drywall. The repairs typically aren't expensive, but risk of hand fracture makes the practice inadvisable. For comparison's sake, punching a hole through drywall is much easier than breaking a wood plank with your fist, as you might do in a martial arts program, but that's not always the case.
Drywall comes in several thicknesses. The thickest is 5/8-inch drywall, which resists fire better than thinner types. Generally, builders use 5/8-inch drywall in garages, around heating systems or in any other room where inhibiting potential fires is a concern. Punching through 5/8-inch drywall is harder than through thinner types.
The thinnest drywall in your home is likely to be 1/2-inch drywall, which is the standard for most residential construction. However, 1/4-inch drywall does appear in some homes, especially if the builders cut corners during construction. Most builders won't use 1/4-inch drywall because of its fragility. Punching through 1/4-inch drywall is the easiest.
Even the thinnest drywall can be dangerous to punch if you don't know what lies underneath. Your home has multiple, parallel wood studs that serve as a frame. Builders attach drywall to the frame using screws. If you happen to punch a section of drywall that has a wood stud directly behind it, you will not break the drywall. Instead, you might break your hand.
Punching hard surfaces can lead to hand or finger fractures. One common injury is a fractured distal fifth metacarpal, or boxer's fracture. The bone within your hand that connects your wrist to your little finger breaks, necessitating casting or splinting. In extreme cases, surgery is necessary to return the bone to its original condition.