How about SSH sending 100 IP packets on each keystroke?
In a similar vein, I recently ran into trouble upgrading Dovecot from 2.3 to 2.4.
There were lots of problems in this upgrade. For starters, Dovecot rewrote the configuration file syntax without incrementing the major version.
Then, they deprecated mbox support.
But the nastiest part was that when configured with pam authentication against system users, they run their own throttling service in parallel with the throttling done by pam in faillock.