If you're in zero g and not on a surface with friction to push against, you're not going to be able to do what a hammer thrower can do standing on Earth. But,

If you're in zero g and not on a surface with friction to push against, you're not going to be able to do what a hammer thrower can do standing on Earth. But, if you provide some momentum to an object like a hammer and release it, you will move. That goes back to "you need to leave something behind in order to go somewhere."