[tootie]

ffmpeg and curl are two open source products I just tip my hat to.

[1-6]

FFmpeg, curl, and NumPy epitomizes the concept of “Do One Thing and Do it Well.”

[radlad]

What exactly is ffmpeg's one thing?

Or curl's for that matter?

[whatshisface]

Curl's "one thing" is to get files from the network in every conceivable way possible. Ffmpeg's is to convert media files between every conceivable set of formats possible.

[kblev]

Curl does loads of stuff, supports so many protocols - HTTP, LDAP, FTP etc.

[corobo]

CLI video editing

Make web requests

[touisteur]

ImageMagick and gnuplot.

[AndrewUnmuted]

GraphicsMagick is like ImageMagick but much more sane & performant.

http://www.graphicsmagick.org/

[rbonvall]

I'd add Pandoc to all the ones mentioned in sibling comments.

[agumonkey]

jq is a neat young one on this list I think

also at the metalevel, gnu parallel

[jmathai]

I'd like to add exiftool to this list.

[KishanBagaria]

+ jq, youtube-dl