I've had a great year, no complaints, so it's tough to just pick one.
Most of my purchases this year are within the top 15-17 rows of pg 1 in my FlickR link below, and some of those were tough to come by and afford.
Many in there I am especially glad to own, Erautt, Baker, Gordon, Aloma, Sisti, Sleater, Pesky, Brecheen, Carrasquel, Ross, Surkont, to name a few, but since it's only one, I will have to say my 52 Topps Duke Snider card is the card I am most happy about purchasing.