the most popular tuning for cajun accordions is for instance, on a C accordion. E's and B's 15 cents flat and all F's 15 cents sharp. Acadians are tuned this way.
Tuning is a touchy subject.
Most "Cajun tuning" I have seen is mainly the E's and B's like Joe says. Marc is one of the few folks that also tunes the F's from what I have seen.