So many possible answers, but I'll limit full discussion to these three, which both pleasantly surprised me as well as improved my scores:
1. Star Mirage - wasn't even planning to try it, but got a proto-star at a discount price. I am still amazed how far this thing glides on a laser-straight path at 50% power on the throw. And thrown with more power, it goes the distance of many understable mids.
2. TP Harp - most recent 'discovery', though I'd thought about getting one for some time. Once I did, it filled the OS approach niche perfectly. In conjunction with this, I learned the more proper uses of the Star Stud, so both discs thrown properly are saving me strokes.
3. Nate Doss Titanium Buzzz - saw Doss throwing his at DeLaveaga and used my PIAS freebie card to get one. Put it in the bag for tryouts and it has done so well that I can't keep it out of the bag(!). Holds hyzer lines with just the right amount of glide for certain holes on my home course. Goes very straight through tight tunnel shots, especially after it began seasoning in, but doesn't turn over or 'drift' right on RHBH throws. Decent forehand disc, ass well.
Honorable mentions: Champion Banshee, Champion Sidewinder.