Transmission is a cross-platform BitTorrent client.
Tor
The Tor software protects you by bouncing your communications around a distributed network of relays run by volunteers all around the world.
Popcorn Zäit
Popcorn Time streams free movies and TV shows from torrents.
OnionShare
OnionShare is an open source tool for securely and anonymously sending and receiving files using Tor onion services.