I think badminton has helped me A LOT in generating serve and overhead power. I'm not a big guy (5' 7" 145lbs) and have only played for just over 1 year but I can hit about a 100-108mph serve all day (at least the radar gun at the last tournament measured it that way). It's such a relaxed motion for me that I don't feel fatigued much hitting 2 baskets worth of balls before a group class.
This slow motion video is very good at showing the wrist motion on a jump smash and it is very similar to how I take swings at overheads and serves.
He holds the record for fastest smash in a tournament @ 332kph (206mph). Sure it slows down but try to fish that up when you are standing about 18 feet away without it hitting you or the ground.