Note: All copied from STO Wiki (consolidated here):
The first style of melee combat is Martial Arts (Unarmed). This is activated by using a weapon slot with no weapon in it giving you access to your Martial Arts attacks. Martial Arts attacks are typically faster and harder to interrupt then their Bat'leth counterparts as well as having additional debuff affects but do less damage per strike.
--1 Jab: Has an 80% chance to Interrupt, 10% chance to Expose.
-11 Chin Strike: Root for 1 sec, 10% chance to Expose.
112 Hay-maker: +300% Critical Chance. Exploit attack.
-12 (Unassigned or unknown)
121 Combined Fist: Knocks back targets in forward cone 3 feet, 10% chance to Expose.
122 Spin Kick: AOE and Exploit attack.
221 (Unassigned or unknown)
-22 Backhand: Root for 1 sec, 10% chance to Expose.
--2 Punch: -100% run speed for 1 sec, 10% chance to Expose.
-21 Uppercut: 80% chance to Interrupt.
211 Knife Hand Chop: Basic damage + Stacking DoT.
212 Snap Kick: Disables target for 3 secs, 10% chance to Expose.
The second style is Bat'leth combat, these attacks typically hit harder then their Unarmed counterparts but are easier to interrupt as well as having fewer debuffs.
Note: Combo information is incomplete due to testing limitations. Also, modifiers do apply to the Bat'leth (See for details: http://sto.gamepedia.com/Klingon_Bat%27leth).