Keypirinha - A lightning fast and flexible keystroke launcher for Windows. No installation required (portable).
Everything by Voidtools - Everything. Locate files and folders by name instantly. Everything. Small installation file. Clean and simple user interface.
Listary - Listary is a revolutionary search utility for Windows
DocFetcher - DocFetcher is a portable German/English open source desktop search application.
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.
X1 Search - X1's Lightning-Fast Search Software. Premium Alternative to Windows Desktop and Outlook Search.