dmenu - dmenu is a dynamic menu for X, originally designed for dwm.
Keypirinha - A lightning fast and flexible keystroke launcher for Windows. No installation required (portable).
Gnome Do - Simple, sleek, swift, smart. Do. GNOME Do allows you to quickly search for many items present on your desktop or the web, and perform useful actions on those items. GNOME Do is inspired by Quicksilver & GNOME Launch Box.
Listary - Listary is a revolutionary search utility for Windows
Gnome-Pie - Gnome-Pie is a circular application launcher for Linux.
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.