Everything - Everything. Locate files and folders by name instantly. Everything. Small installation file. Clean and simple user interface.
DocFetcher - DocFetcher is a portable German/English open source desktop search application.
X1 Search - X1's Lightning-Fast Search Software. Premium Alternative to Windows Desktop and Outlook Search.
FSearch - A fast file search utility for GNU/Linux based on GTK+3
TextSeek - TextSeek helps you search document contents for Windows and MacOS within seconds, including PDF, Word, Excel, PowerPoint, and other formats.
AstroGrep - AstroGrep is A Microsoft Windows GUI File Searching (grep) utility.