IMO, Kali (a Filipino martial art) is the best. Although not a weaponless art, but you can always find an improvised weapon. This is particularly important, because, in an actual combat, you are likely to be outnumbered.
Aikido. I'm small, and I like the idea of using an opponent's energy against him, while expending little of my own. It's not an attacker's martial art, it's defense based, and I admire the concept of defense without attacker's aggression.
Krav Maga. If you're going to fight, then the point isn't to subdue your opponent. It's to hurt them so badly that they remember not only the humiliation, but the outright pain involved.
Half of the techniques in KM start with a low blow. There are no rules. Things like eye rakes, throwing sand in someone's eyes, and all out just fighting plain dirty are absolutely encouraged.
And considering the human body has so mean weak spots and ways to shatter important bones or knock out/kill in short order, it shouldn't be too difficult for someone skilled in KM to destroy someone else. And for all of these grappling type martial arts, guess what? If a guy is on your back trying to get a chokehold, punch him in the nuts. Gouge his eyes. Take control of one of his fingers that's not yet locked in and bend it and shatter it.
All of these things are outright illegal in MMA due to the danger they have of permanently injuring someone.
But if you're going to fight...
ISN'T THAT THE POINT?
Aikido. I'm small, and I like the idea of using an opponent's energy against him, while expending little of my own. It's not an attacker's martial art, it's defense based, and I admire the concept of defense without attacker's aggression.