I guess I should go ahead and nominate ...Volkl V-square is the spinniest string I've ever played with. If you're into spin, it's a lot of fun.
which I'm installing as mains in hybrids with good client feedback. I always like square shapes for wear & bearing surface reasons and the 4S 1.25 mm has been a worthy performer (so far, tbh, since I'm not quite through about one-third of a reel yet).
I like it.