One BIG thing missing: xteddy! It was xteddy shown in parallel on multiple HP 9000 screens in the early 90ies, which sparked my love for UNIX.

http://weber.itn.liu.se/~stegu/xteddy/

see also

https://xteddy.org/

Also xon (very handy for non-ssh users), jwz's xdaliclock and xkeycaps.