The answer is, almost all of it. In space if you try to poke someone in the eye, you will both spin away from each other. However I think you could poke a persons eye if you were simultaneously pulling them towards you by the neck. Anyway nearly all strikes, kicks and throws are gravity dependent. Probably about 70% of joint locks are too. Most of them would be impossible to get on a resisting partner in space. Even hair pulling is out. We are left with squeezing grabs to the groin and neck--and head locks.
Since everyone knows, space is the next wild, wild west (Firefly fans?), I think we should start training for zero gravity fighting.
It’s also a good way to explain why relaxation is superior to tension in a fight. Almost everything we do in a fight is gravity dependent. The best fighting methods force an opponent to carry not only their own weight but your weight too, at the worst possible angles. Even with throws in which the opponent is picked up into the air, momentum is used in combination with a destabilized base to create a circular force around a center of gravity and a gravity dependent still point--ending of course with a smack down. (I just wanted to say smack down.)
So start analyzing fighting methods in terms of gravity and they will become more effective. As long as you are controlling the exchanges of momentum, your opponent should be carrying as much of your mass as possible. So, for example, if you punch someone you want all of your weight to hit them with momentum. If you do it right, strength is completely irrelevant.