Here is a link to some ideas. There are commercial products out there to do the job. Some are listed in the link. http://lifehacker.com/5897807/how-to-remove-rust-from-old-tools
You can find may more ideas and methods using Google. You can even use electrolysis to reverse the action of the rust.
Except for electrolysis, I would stay away from water. That's what causes the rust to start with. Be wary of any method that involves a lot of scratching like wire brush, emery paper etc. It depends where it is on the tool. Adding scratches to the face of a stamp, or abrading the pattern is not something you want to do. Brass brushes generally won't damage steel surfaces since the brass is soft.
Be cautious of strong acids and other chemicals.
With all the different rust removal methods out there, think about what the results are that you want, use some common sense, and you should be able to reclaim these tools without causing further problems.
Tom