Keyclone - Keyclone is a key broadcasting application that allows users to control multiple instances of an application using a single keyboard/input device. While commonly used for m...
Synergy - Cross-platform software for sharing your mouse and keyboard between multiple computers
ISBoxer - Play characters together. Powerlevel yourself. Multibox.
Input Director - Control multiple windows systems with one keyboard/mouse. Share a keyboard and mouse across multiple windows system.
HotkeyNet - HotkeyNet is free multiboxing software.
AutoHotkey - The ultimate automation scripting language for Windows.