Great thread!
I miss the days when all nine players in the field took their turn at bat, i.e. according to the original intent of the game.
I miss the days when a player actually had to touch first before he could get to second in extra innings.
I "miss" the deadball era when players tried to hit the ball into gaps and turn singles into doubles and doubles into triples. I miss all the base stealing that was part of baseball back then. I miss all the action on the basepaths.
I miss knuckleball pitchers.
I miss the Tampa Bay Devil Rays and their wild cool uniform.
I miss the Montréal Expos and the Cleveland Indians.
I "miss" Ty Cobb and the intensity with which he played the game.