The "Corps Francs" or "Groupes Francs" were volunteer shock troops formed from standard infantry and cavalry units during the Phoney war to patrol the no man's land and harass the enemy. The units were often platoon-sized, sometimes company-sized.
Some were kept in existence during the May-June 1940 campaign. The "Groupes Francs" used standard French weapons but also some unusual equipment like shotguns and a few SMGs.
I don't know any ASL scenarios, official or TPP, with "Groupes Francs" but I have a few designs with some.
The well-known French magazine "Militaria" had an issue with a large article about the "Groupes Francs", n°179, June 2000. It's mostly about uniforms and equipments but there is also very precise data about weapons and some actions. But it's in French ... take a look at histoireetcollections.com.
One known english-language source is the Osprey MAA n° 315 "French Army, 1939-1945 (1)".