1)GAINING SOME ADDITIONAL KNOWLEDGE,which can't be found in normal web.
2)To browse torrents sites.
3)To do some serious Crime.
4)drugs.
5)porn.
6)anonymous emailing.
7)bitcoin mixer or tumbler.
8)understanding all types of fraud.
9)downloading a premium software free,which is costly in normal web.
10)politics,dark GOD,GUNS.............