Ooh la la! Dalila Ayoun, a professor in French Linguistic, found that native French speakers can't agree on the genders of French nouns:
Fifty-six native French speakers, asked to assign the gender of 93 masculine words, uniformly agreed on only 17 of them. Asked to assign the gender of 50 feminine words, they uniformly agreed only 1 of them. Some of the words had been anecdotally identified as tricky cases, but others were plain old common nouns.