Answer:
Depends. I would say a book.
Step-by-step explanation:
If I were an enslaved person in the Americas during the times of slavery, there are good chances I wouldn't be able to read. However, I would seek to teach myself or to learn eventually... if I was able to get my hands on some volume.
If I was seeking freedom, my future and my ability to take a stand in the issue and help other enslaved or formerly enslaved individuals would largely reside in my educational background. All of my prospects would lie in my ability to speak, write and communicate.
If it was not "the most special" item but the most practical, then perhaps I would take a weapon or tool.