Marksmanship
*bump*
I'm not just being snide ala "gun beats swords indana jones hahahah!!1!"... Effective marksmanship is a martial artform, by definition. Modern ballistics make things much more accessible, but historically, archery played an arguably greater strategic role than close quarter melee.
For example, the longest living and most revered Samurai were those whose aptitude for nailing targets from a fast moving horse, often turning the battle for their masters.
I suppose I'd like to see it considered more as a martial study than it is, but respect due to all the other disciplines.
One that stands out for me is Krav Maga, the IDF's professional "dirty fighting to save your life" principles refined to protect the lives of their soldiers on a modern battlefield.