Sorry RMiller, but I'm not going to let this go to the bottom of the pile. So, I'll post my 2 cents. I feel your question is a difficult one to answer. Although in 2007 Tuff Stuff magazine broke down what they felt were the "Holy Grails" of collecting. The article went from cards, to autographs, Hartland statues, and yes.....even baseball gloves. Their choice was Mickey Mantle's gamer from the 1956 season. The same season the Don Larsen perfect game took place. Were they right? To some maybe... to others maybe not. I honestly don't think there is a Holy grail item in glove collecting because everyone has different taste and different budgets.
Although I think there are gloves that provide a lot more notoriety in someone's collection and turn more heads if he/she has that particular glove like the T206 Wagner (which in reality isn't that rare compared to some cards in the hobby) does for card collectors. I'd say any of the following can elevate your collection significantly in the eyes of most glove collectors (quality considered) Fingerless, duckweb, Ty Cobb glove, Ruth G41, Gehrig ken wel Zipper back, and any gamer from the first hall of fame class.
Thoughts?