Depends on the day.
I really want to say my Swords. I have been having issues getting my wrist to fire recently and thus have been having troubles getting snap into my drives. This means a lot of wrist rolls and grip locks. The Sword basically is a very not-descript driver when this happens. Yet when I nail the line and get that snap, the Sword is the straightest, meanest maximum distance driver I have ever seen. I want this disc to be my main driver. Right now it shares duties with a Pro Destroyer when I am unsure of the situation and whether I can generate snap on that given throw.
Star TeeBird. The heavy Gold Line Rivers were my good-to, jaw-dropping fairway drivers for over a year. Ever since I smacked a tree backhanded at full force, the River has not flown right out of my hand since. The TeeBird with its modestly more LSS helps me by being able to handle that extra muscle I sometimes put into the throw to compensate for less snap. Right now I am rocking a new heavy Star TeeBird and a light and beaten Star TeeBird that covers almost all of my fairway shots. I have had four ace runs with these TeeBirds in the last three weeks, every time missing by no more than a foot. I still keep a River in my bag so I can continue to practice in hopes to get back to my old form, but its role has been diminished to stand and deliver upshots.
Star Ontario Roc. I can drive and approach with this disc with very good, almost deadly accuracy. I have had several ace opportunities jump out of the chains with this disc, once during one of the biggest tournaments of the year and while I was sitting on the top card. Just hitting the chains of course makes me feel good that sometime I am going to be seeing several of them going in. I do not necessarily like the grip of the Ontario Roc, but I cannot complain with its results. Right now with the issues I have been having with my drivers, having an accurate 2nd shot is the only thing keeping me remotely competitive.
R-Pro Polecats. This is such a glidy, neutral disc that it is tremendously fun to throw. It shares the putting duties with Organic Wizards, and depending on the situation, the potential the Polecats give me for running the basket from almost any approachable distance makes these discs so much fun to throw. With a stack of them I could spend an hour or two at home on my portable just running the basket from 100-120 feet out.