get a gun.
if not, go for either brazillian jujitsu or muay thai. those are the only two applicable martial arts. everything else SUCKS. period.
-aikido takes like at least 6 years to master, if you haven't mastered it, you're gonna get your @ss creamed on the street.
-taekwondo is a $hitty martial arts, useless on the streets and only good for performing on stage.
-kung fu (especially wing cheung, it was developed by a woman) is also useless on the street.
-karate is useless too.
jujitsu is useful cause most fights end up on the ground, people only box for like 5 seconds and then they'll tackle you down to the ground. muay thai's concept is all power. everything you do (kick/punch) has max power in it. on the street, only a muay thai kick to the leg is useful. some stupid karate tap tap side kick or kung fu tiger claw isn't gonna do jack to some guy that weighs 180 lbs and you only weigh 140. trust me, i've taken karate AND muay thai before and there's a huge difference.
if you decide to go with muay thai, make sure you talk to the owner and make sure he doesn't feed you cr@p. if he starts talking about zen and chi and all that mental bullsh*t, leave. if you go into a place and see people practice toughening up their shins by banging stuff on it and kicking each other on the shin, that's the place you want to study at. that's the real deal.