Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
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.
YAATA - YAATA app offers features that let you send multimedia files such as images, videos, audio, and GIFs, etc.
Axcrypt - AxCrypt - Password Protect Files With Strong Encryption. AxCrypt is the leading open source file encryption software for Windows.
Enigmail - Security extension to Mozilla Thunderbird and SeaMonkey
Microsoft BitLocker - BitLocker is a full disk encryption feature included with Windows Vista and later.