Firstly, apologies if I've spelled 'guerilla' incorrectly!
Secondly, a major bugbear of mine is the substitution of 'less' for 'fewer'
so
I was at the council offices this morning getting some parking permits and while the girl was getting them I noticed on the desk a pile of surveys for people to fill in with an instruction [for the official] that each office must collect no less than 200 surveys etc etc. And I found my pen and on the top copy crossed out 'less' and wrote 'fewer' above it. I did it twice but then the girl came back and I had to stop.
It felt fabulous, but I'm insane, aren't I?