Brazilian Jujutsu practitioners like to say that most fights end up on the ground, which may or may not be true, but what is true is that fights aren't that clear cut - most people have friends, and their friends will join in, in which case being on the ground is the worst place you can be since you can't defend yourself adequately from a standing attacker. Out of those options, I would go with jujutsu.
Karate is a great art and I really like it, but it is primarily taught in kata (sequences of choreographed movements intended to transmit techniques and concepts) which will not be immediately applicable. Karate that is taught in a more hands-on way will usually still be points-based, and training in those kinds of competitive rules-based environments can do terrible things to create unwarranted self-confience in your abilities to handle yourself in real-world altercations.
Taekwondo is a Korean martial art that focuses a lot on kicking due to its development roots. Check out some Youtube videos to get a feel for what it's like, but personally I don't find it very appealing, mostly because of its emphasis on distance - there is no real grappling element to taekwondo which means that if an opponent closes distance on you, you will not be well-equipped to deal with that situation.
Jujutsu however, though there are many, many different styles, often teaches both long- and mid-range situations (which require striking) and close-range situations (which require grappling, locks and take-downs). Depending on the club (and faithfulness to historic roots) it does not necessarily focus on a competitive element, where techniques must be necessarily limited due to the damaging nature to the aggressor. Specifically, koryu styles focus directly on the teachings transmitted to previous generations (and members of the Samurai class in Japan) which were purely about efficiency (necessiraly as their applications were usually to be employed in life-and-death situations) and so they lesser take into account the well-being of the aggressor (which is required in competitive sports). The drawback of this is that you need to be conscious to a certain degree which techniques you are taught would be permitted reasonably under a self-defence scenario.