Maybe not "the prettiest", but your favorite. Please post an example, if possible. There are a few I like. While Ruth and Mantle are both very classic and eyecatching, I think Lou Gehrig's is just beautiful. Very fluid.
But one that just visually appeals to me and I don't know why is Bob Lemon. He normally signs smaller than most players on multi signed items. I just like the slant he had to his signature. I think something in his signature reminds me of my grandfather's (also named Bob), who recently passed away.