For French, we usually sing 'Chant du Depart' or the Marseillaise. 3eme aren't really big singers, the 85eme for example sing a lot more.
I'm trying to learn 'Den Keyzer, Oranje en Chassé', a Dutch song which is quite nice, for my Dutch Hussar impression. I also try to learn 'Fanchon' and 'Aupres de ma blonde', which are French but are historically not incorrect for the Dutch to sing.