I have a fair amount of certified auto cards but my favorite set is Upper Deck's 2005 Signature Decades. Overall the design is appealing and they are all on card autographs in a bright blue ink that stands out nicely against a white background.
To begin, here are my 2000's and one 1990's. For some reason there are very few of the 1990's series out there. Will Clark is my only one and his is serial numbered to 99. (The serial number is on the far left on Will's right arm.)