My personal favourites from Finnish.

"Ei ole kaikki muumit Muumilaaksossa" "Not having all the Moomins in Moomin Valley" Used for people who are either stupid or lack sanity. There are other variants of this and Moomin one is not older than a couple of decades.

I find our version of Grammar Nazi pretty great. We call them comma fuckers.

"Ei voi kauhalla ottaa jos on lusikalla annettu" "You can't take with a ladle if it was given with a spoon". This refers also to a lack of something, usually a lack of intelligence or sense.