My favourite one is already on there:

https://openbenches.org/bench/5849

"Nina Theresa Jenkinson 4th of May 1959 - 5th May 2017 She took pleasure in annoying the fisherman by feeding the ducks"

(it's by a private fishing lake within a public park; I don't know if she just liked feeding the ducks (but she could've done that many other places nearby) or if it was a passive aggressive demonstration against catch and release fishing, or against having a private lake there, but either way I find the inscription is memorable)