PuTTY - Popular free terminal application. Mostly used as an SSH client.
Beyond Compare - Beyond Compare allows you to compare files and folders.
MobaXterm - Enhanced terminal for Windows with X11 server, tabbed SSH client, network tools and much more
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
iTerm2 - A terminal emulator for macOS that does amazing things.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.