What's the best open source app or utility that no one else has heard of?

(Please note that your replies may be read out and discussed on an episode of Late Night)

#VoiceOfTheMasses

@LateNightLinux mosh. It's an ssh replacement that handles intermittent connections, jobs you start on the remote machine will continue to run even if you lose connectivity. https://mosh.org/
Mosh: the mobile shell

Mobile shell that supports roaming and intelligent local echo. Like SSH secure shell, but allows mobility and more responsive and robust.

Mosh