KeyCue - Menu shortcuts are supposed to provide quick access to frequently used menu commands.
Pretzel - Keyboard shortcuts for the app you're currently using
CheatKeys - View Windows keyboard shortcuts in the current application.
cheat - Cheat allows you to create and view interactive cheatsheets on the command-line.
Alfred - Alfred is an award-winning app for macOS which boosts your efficiency with hotkeys, keywords, text expansion and more. Search your Mac and the web, and be more productive with custom actions to control your Mac.
KeyClu - Learn and use all shortcuts easily