Melee Kata - Press both attack buttons at the same time Flying Kick - Hold Use, Forward, Attack 2 Leg Sweep - Hold Use, Crouch, Attack 2 Uppercut - Hold Use, Forward, Attack 1
I believe what you are referring to is the "Melee Katas." There are three of them and they can be performed with the direction keys.
To grab someone press both mouse buttons.
Right before you grab a person press one of the following:
W or Forward = A grab that perform a series of punches to the stomach
S or Backward = A grab that tosses the enemy multiple times from back to front
While an enemy is behind you = Throw an enemy over shoulder