Twithaca is a retweet bot on Twitter that automatically retweets all tweets with #twithaca in the text.
I did not create it originally, but I did assume ownership and stewardship of it after it broke when Twitter changed its API in 2012 (I think?). Originally, it was written in PHP and when I took it over, I re-wrote it in Ruby, using sferik’s Twitter gem. I wrote a quick-and-dirty Ruby script that would mimic the functionality of the original, then set up a Cron job to run every 2 minutes and handle the re-tweeting. It worked for a while.
Eventually, I refactored the code to generalize its usage outside of just #twithaca, and wrote some RSpec tests. This became the Twitterbot gem (link below).
It now has features such as automated blocking (blocking a user as the authenticated account will also skip retweeting tweets by that user).