what fighting style do you recomend to practice for a month ? (karate,kunfu,tai chi)?

All the martial arts you have listed require commitment, so joining for a month is maybe not the best idea - I mean, I've been doing karate now for 6 1/2 years!

Martial arts are good at improving self confidence, but you would need to be a member of a club for a few months to actually go up a belt..

boxing