I have done quite a few martial arts. I have black belts in two styles of karate and used to be a karate instructor at the Oxford University Karate Club.
I've done Shotokan, Wado Ryu, Goju Ryu, Kyoku Shin Kai, Shito Ryu (no, I didn't make it up!), Tae Kwon Do, freestyle karate, Lau Gar Gung Fu, Jujitsu and... ehem... ninjitsu (insert scornful cough here).
Karate is great for all-round fitness, mental discipline, coordination and fighting technique. It's approximately 50:50 kicking and punching. Most karate styles don't involve much contact... Touch contact, or semi. Some are full contact, like Kyoku Shin Kai and this is quite gruelling.
Shotokan is a very 'strong' style with much focus on tradition. Wado ryu is also traditional, but also has a strong focus on 'competition' karate.
However, it's not all that good for self defence since karate-ka (people who 'do' karate) like to keep at kicking distance and this doesn't really happen on the street!
From a self-defence standpoint, jujitsu is by far the best martial art to take up. It involves locks, breaks, throws, chokes and strangle holds. Furthermore, you get to do a lot of groundwork, which is where most street fights end up. It's much like aikido, but is more aggressive and more direct.
Many of these arts (especially jujitsu) have some focus on weapons. My personal collection involves two katana, one bo staff and a set of nunchaku.
Ninjitsu is a crock. I've done a little and read several books, but it's not a true martial art! It's like jujitsu, but extremely diluted in content and technique. They spend far too much time focussing on mysticism and not enough on real technique.
So, my view... If it's about fitness, technique, and self-improvement, then you can't go wrong with something like Shotokan karate.
If it's about self defence and how to do some serious damage, gotta be jujitsu!