The single most important body part for fighting is midsection by far. You would be surprised as to how much leverage you get from that. A strong midsection makes it much easer to through people around.
Then delts. a strong punch is in the delts and triceps. chest is pretty useless, it is used for bench pressing and not much else.
back is also a very important for any type of heavy labor including wrestling.
do deads, squats(they help with EVERYTHING), bench(power lifter syle, bb has almost no functional strength) OHP, cleans, upright and bent over rows.
Obviously it is better to look invincible first so that you rarely have to fight. i have a very easy time intimidating people because of the way i am proportioned. I only weight 212 but my delts and back make me look allot bigger.
I am gana start learning judo as soon as i find a good school for it since everyone seems to think it helps alot.