Just found this when Googling for swear words in German (for reasons I shan't go into at this time, but, I assure you, with the best of intentions. *Ahem*.) :
Swearsaurus : How to swear, insult, cuss and curse in a wide variety of languages. Too bad the Latin ones are mostly made up.
Antiquis temporibus, nati tibi similes in rupibus ventosissimis exponebantur ad necem
"In the good old days, children like you were left to perish on windswept crags."
has a nice ring to it.
Oh, and I like this one in Polish:
Czys ty sie z chujem na glowy pozamienial?
Have you changed heads with your dick? (Are you nuts?)
Mermelada de huevas -- "Testicle Jelly", an extremely idiotic person (Chilean Spanish).