It depends on the path of electricity
The effects of the electric shock depends to a great extent on the path of electricity as it moves through the body. If the current moves from an arm to another it can pass through the heart and so can be very dangerous.
Burns can happen
The resistance of the body will result in the production of heat which can lead to burns. In such a case, burns might be obvious on the skin.
Burning internal organs
According to Wikipedia, if the voltage is above 500 then internal burns might occur. An organ inside the body, or more than one organ, might get completely burned as a result of the heat. (See How does burning to death feel like?)
Loss of muscle control
The flow of current in the body can force muscles to contract and so prevent the person from moving the muscles subjected to shock.
Electric shocks in the chest can be lethal
An electric shock of 110 volt in the chest can affect the operation of the heart’s muscles causing a condition called ventricular fibrillation that can cause death if not treated quickly.
The heart might stop
If the current reaching the heart is high enough, the heart might stop and the person might experience a cardiac arrest.
Damage to nerves
If the shock is strong enough then some nerves might get damaged causing a condition called neuropathy which might result in impairment in sensation or movement.
Loss of limbs
If the current is strong enough, it might cause damage to the muscles. This could later lead to amputation.
In such cases cognitive damage might happen. The person might experience memory issues or even serious changes in his personality.
Messes with the nervous system
The human nervous system uses electrical impulses to communicate with the different parts of the body. Any external electric shock might interfere with the operation of the nervous system and cause undesired effects such as involuntary urinating, for example.
Electrocution or death
If the current is strong enough then electrocution or death by electric shock might happen. Each person might die because of a different unique reason as different organs might get damaged. (See What does it feel like to die?)
What happens to your body when you get an electric shock?
The effects of an electric shock on the human body | What happens to your body when you get an electric shock?