I know a few doormen and a few ex doormen who do sets of rounds on the bag each day without gloves to condition the knuckels making them stronger. The connective tissue does grow stronger despite what people may say. I haven't used a closed fist on someones head myself in a real go since my younger days. I am a strong advocate of palm strikes due to the fact you have a greater chance of scoring a KO due to the larger strike surface. A punch has to be pretty accurate and if it is off slightly will only glance and not cuase damage. Prime aim in a real fight is to switch the machine off at the mains as soon as possible. Palms are better (IMO)

Having said this if you connect right with a punch on the jaw then you won't hurt your hand. Its what is called the butter punch because it feels like you could be punching through butter. BUT add in the factor of adrenaline in a real fight and targetting gets f*cked and 9 times out of 10 punches rain down and glance off the skull causing little damage. Generally only a skilled exponent has any real success.

Anyway in a real fight hit first and hit hard. Munk3y...train combative palm strikes for seeing off nutters mate.

nb. I in no way condone violence of any sort