Ça a sa petite volonté (fam.) = It has a will of its own (in speaking of children, etc.).
C’est toujours ça = That is something, at any rate.
Pas plus que ça?; Rien que ça? = Is that all?
[This is generally used ironically: e.g. Le cocher m’a demandé vingt francs pour aller de la Place de la Concorde à Longchamp!—Rien que ça?]
Cabinet
Cet avocat a un bon cabinet = That barrister has a good practice.
Cachet
Courir le cachet = To go from house to house giving private lessons.
[This expression comes from the custom of the master giving to the pupil a number of tickets (called cachets) at the first lesson, for which the pupil pays, and gives one back at the end of each lesson.]
Cadet