Let us first go to the Holy Tome:
Martial Artist;
Can fight unarmed very effectively (using karate, kung-fu, aikido, jiu-jitsu, savate etc.) - see Weapons Table.
Also gains a bonus of +1 to Speed.
Weapons table
Unarmed (martial artist) FV+1 Pluck +0
Our intention was to give a person an effective attack using bare hands, elbows, knees and feet. So Martial Artist is an attack weapon in and of itself. Figures armed only with shooting weapons or who have lost their weapon to a fumble can thus fight without having to resort to fisticuffs (FV+0, Pluck +1).
It also gives you greater speed which, as we know, gives you an improvement to your defence when fighting, as the figure blocks and dodges their opponent's attacks.
It does not give a bonus to any handheld fighting weapons.
However, a martial artist with a decent FV and a pistol is a dangerous foe. They can shoot the pistol while in a fight in the shooting phase, then either concentrate their fists of fury onto a single opponent or split their attacks between two or more....