Muay thai is a lethal strikin art. Uses the 8 point technique, utilizing hands, feet, elbows, knees. Highly telegraphed moves though, so if you are faster, or have techniques for that, such as in Aikido, this isn't as good in my opinion. Very brutal.
Close up skull would be a good tattoo, with something hidden in the eye. city scape, comic book scenario/villain, doctor who reference etc. Thigh/side/leg/upper right arm (ribs maybe? but PAINFUL)