I collect Toronto Blue Jays Memorabilia. In terms of tradition, antiquity, and overall aesthetic appeal, Blue Jays stuff just can't be beat. JK, of course... I don't think I have ever seen a Blue Jays post here, so just wanted to break the drought
Seriously, I collect Philadelphia Athletics (pre-war), and Cincinnati Reds (post-war). Philly A's because they had such iconic teams with players like Foxx, Simmons, Grove, Baker, Collins, Plank and Bender (not to mention Connie Mack at the Helm). Plus, the White Elephant Mascot made for so many cool collectibles.
Reds because I gew up in Cincy, and witnessed the birth of the Big Red Machine. Plus I got to attend the final games played at Crosley Field (my first experiences with baseball). The '75/'76 Reds were (IMO) the greatest offensive squad ever put together, and perhaps even the best team ever.
As for the players I collect... Ruth, Gehrig, W. Johnson, Mathewson, T. Williams, and the greatest
Clutch Hitter of my era... Tony Perez.