I have a $100 voucher from a cancelation I've booked about 20 tickets off of and still have $65 left. (Which that cancelation was happy luck - I wasn't going to take the trip, so I checked in and picked a Stretch seat then no-showed without even getting out of bed because, well, Frontier deserves that sometimes... my luck I woke up to find the flight canceled and a voucher)

I got a $50 voucher for sending them photos of a vendor supervisor at CLT screaming at passengers including telling Elites (well, all two of us) we aren't entitled to any "special treatment" and could board with our zones. That one was good for the entire total. But, like another mentioned was their experience, I had the itinerary I booked with it altered so that Frontier had me flying both directions of my trip at the same time (and the text agent didn't seem to see the issue with that), so got a refund, then booked again, to have the schedule change mess up that trip, so I think I finally used it on a third trip.