Supposedly, the saddest of all possible words are "Tinkers to Evers to Chance". I don't know since I never saw their version of the 4-6-3.
Still, that's not my favorite play, even though it is prettier than the 6-4-3. All fluidity and beauty is lost with the pivot of the second baseman.
My favorite assist play has got to be the 3-1. Simpler, but much more beautiful. No matter how many times I see it, it reminds me of why I love this game.
It shows heads-up play everywhere. From a good glove man at first to a hustling pitcher covering the right side. It takes skill, timing, and tons of practice.
The only thing that makes it prettier is to see the right fielder charging in to back the play up and see the catcher running down the line to back his side up.