Cloaker
Very simple cross-platform file encryption
Cloaker aims to be the most straightforward file encryption possible. Just drop a file onto the window and set a password. To decrypt, select "Decrypt", drop the encrypted file on the window, and enter the password.
Note 1: the Linux version in this release requires at least glibc version 2.25. I don't currently have a static-linking Qt installation on an older machine to build with, but I might be able to set one up if there's need.
Note 2: after a bug fix for the 1.1 release, I forgot to bundle the Qt libs properly for the Mac version and it wouldn't launch. This has been fixed.