GitKraken - The intuitive, fast, and beautiful cross-platform Git client.
cheat - Cheat allows you to create and view interactive cheatsheets on the command-line.
SmartGit - SmartGit is a front-end for the distributed version control system Git and runs on Windows, Mac OS...
cheat.sh - The only cheat sheet you need Unified access to the best community driven documentation
SourceTree - Mac and Windows client for Mercurial and Git.
explainshell - Match command-line arguments to their help.