Firefox. Runs on all the platforms I use (Linux, Android and Windows). Shares state between all the devices I run it in. Been somewhat the same since Phoenix days for me, the end user.

GNU Core Utils. They've been the pretty much the same since I first learned about those.

- VLC: If it can't play it, it's not a video or audio file.

- nginx: It's fast and has a lot of features.

- MAME: Arcade emulator, this project is amazing.

- ImageMagick convert: Wonderful command line tool for manipulating images

- ffmpeg: Wonderful command line tool for manipulating videos

Linux OS. Near perfect OS for developers.