For the wake boats I've been on, short of ballast, my favorites have been fresh air exhaust, and an amp with microphone to input. Using a cb style mic to provide coaching is a great tool. Fresh air exhaust makes it very easy to hear out there. Also makes standing on the transom and surfing much nicer.
I spent most of my money on booze, broads and boats. The rest I wasted. - Elmore Leonard