it all depends on what distance its being thrown from and how its thrown. from 30 feet its got to be the rattler but it could be a challenger when youre throwing it 250, but the whole game changes when you talk about throwing it sidearm or turbo putting. "Whats the straightest putter?" can be interpreted 100's of ways.
Yea like what's has been said before no real answer can be givin. Do you loft putt, spin putt, turbo putt. I would say omega putter, but others good one are magics, or "caughWarlockcaugh". If your not putting alot of spin on your putts stick with small bead or beadless putters.
the Latitude 64 Pure is very straight. It's a great approach disc too. It seems like a good one for spin putting. (personally I like overstable putters like wizards and kcs though). yeah, Warlock too, very straight.