let me re-frame the question using an example...
What are the bare minimum components you need for example to run the test application simple1 (found in the crystal space installation directory). such that if i put these components together with the simple1 application in a separate folder, it would run without any qualms.
As Jorrit already said, that's hard to answer. In fact, offhandedly, we don't know the exact list of these plugins ourselves; we would have to find it out first, using the techniques we described in the answers so far.