Keypirinha - A lightning fast and flexible keystroke launcher for Windows. No installation required (portable).
Scherlokk - Mac OS X application. Simple and user friendly, Scherlokk will find your media and missed files - quickly.
Listary - Listary is a revolutionary search utility for Windows
Slingscold - Slingscold is a lightweight application launcher similar to Launchpad in Mac OS X.
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.
kupfer - Kupfer is a command tool heavily inspired by https://alternativeto.