What are symptoms of a cracked head or bad head gasket?

Common symptoms are loss of power, missing cylinders (lost compression), coolant in the oil (looks like a chocolate milkshake), oil/fuel in the coolant (looks like coolant, smells like fuel), noise, overheating, white smoke from the exhaust, air bubble escaping form the radiator, loss of coolant with no apparent leak, and a foamy substance on the underside of the oil fill cap.