Purely idle musings. Systems I wish people would rewrite in #rust:
 - ntpd
 - gpsd
 - postgres

tell me why I'm wrong or what I'm missing. 

(rationale:
  ntpd is critical software with a history of security vulnerabilities and a requirement for tight timing. extensibility would be a very nice thing.
  gpsd for basically the same reasons + ESR.

  postgres because I like it.)