X-Mouse Button Control is a Windows application to remap your mouse buttons and expand the capabilities of your mouse!
SharpKeys is a utility that manages a Registry key that allows Windows to remap one key to any other key. Included in the application is a list of common keyboard keys and a Type Key feature to automatically recognize most keyboard keys. It was developed in C# using .NET v2.
Karabiner, previously called KeyRemap4MacBook, is a very powerful keyboard remapper for Mac OS X. In addition to simple key remapping, it has special remapping modes like Emacs-mode, SandS-mode (Space and Shift).
antimicro is a graphical program used to map keyboard keys and mouse controls to a gamepad. This program is useful for playing PC games using a gamepad that do not have any form of built-in gamepad support.Discontinued
The latest release was on November 5th, 2016. A new generation of the program called AntiMicroX is available.
The xmodmap program is used to edit and display the keyboard modifier map and keymap table that are used by client applications to convert event keycodes into keysyms. It is a part of the X.Org project.
Keyszer is a smart key remapper for Linux (and X11) written in Python. It's similar to xmodmap but allows far more flexible remappings. Keyszer was forked from xkeysnail which no longer seems actively maintained.