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 "Rawhide" ("rh") is a C-like syntax find utility. I have kept it alive over all the years since it first came out in comp.sources.unix on Usenet:

https://sources.vsta.org:7100/rh/index

For instance, C source bigger than 10k:

rh -e '"*.[ch]" && (size > 10K)'

C source or Makefiles modified more than a week ago:

rh -f -
("*.[ch]" || "[Mm]akefile") && (mtime < (NOW - 7*days))

(For longer things, it'll accept the code on standard input, or from a file.)