grep - grep is a command-line utility for searching plain-text data sets for lines matching a regular...

fzy - A better fuzzy finder

PowerGREP - Quickly search through large numbers of files on your PC or network using powerful text patterns to find exactly the information you want. Search and replace with plain text or regular expressions to maintain web sites, source code, reports, ...

skim (fuzzy finder) - Discover open source libraries, modules and frameworks you can use in your code

dnGREP - dnGrep allows you to search across files with easy-to-read results.

Everything by Voidtools - Everything. Locate files and folders by name instantly. Everything. Small installation file. Clean and simple user interface.