Using code generation for your Rails utility scripts (like importing demo data into production) that can then be executed remotely (no need to deploy).
One-liners can be piped into the heroku run console command—what about longer scripts you write locally and want to execute in a remote Heroku environment?
Using replay, replayLast, and replayLazily operators on an infinite signal leads to memory leaks if you're not careful. Be sure to clean up after yourself.