Android: If you want to browse the file system of your Android device, there are plenty of apps to choose from, but FX File Explorer has a feature set that can stand toe-to-toe with the best of them.
If you can think of something you might want to do with a file, odds are you'll find it here. You can split your screen into two windows, select multiple files by dragging your finger, examine them with various view options, and move them back and forth with ease. A robust search feature also helps you find files based on location, kind, date, size and name. FX comes with a basic text editor if you need to make a quick change to a text file.
The base app is free and awesome, but the $2.99 FX Plus Plugin adds some pro-level goodies. You'll be able to create and extract encrypted zip files, network with Windows over SMB, upload and download from FTP, Google Drive and Dropbox, share with other devices over Bluetooth. If you're in the market for a comprehensive file browser, it's money well spent.