Onionshare - OnionShare lets you securely and anonymously share a file of any size with someone.
Cryptomator - When it comes to saving your files on a cloud server, it is important to ensure the security of those files. Keeping your delicate files out of the wrong hands can save you a lot of time and hassle. Read more about Cryptomator.
ShareDrop - HTML5 clone of Apple's AirDrop - easy P2P file transfer powered by WebRTC
Axcrypt - AxCrypt - Password Protect Files With Strong Encryption. AxCrypt is the leading open source file encryption software for Windows.
Send Anywhere - Send whatever you want, wherever you want
Microsoft BitLocker - BitLocker is a full disk encryption feature included with Windows Vista and later.