Of course, there's no better place to start than the Topps rookie card!
Card #: 648
I like that Larkin's rookie card is in the 1987 Topps set - one of my favorite set designs. The card features a decent shot of Larkin on the front and Larkin's minor league stats in the back. The wood border is iconic, and I like that both the team and the player name are easy to see. This is the way a rookie card ought to be (without that annoyingly large "rookie card" logo that card companies slap on rookies now).
Quick aside: I'm always looking for new Barry Larkin cards - if you have any for trade let me know!