Over the last few years I've dragged this ball (which I originally snagged during batting practice at a game in Oakland) with me whenever I attend a game involving the Blue Jays (ironically, never in Toronto), on the off chance that I get a signature or two. It has paid off to the point that I now have eleven different signatures on this particular baseball.
They are a bit hard to make out, but if my memory serves me correctly, the following players are included - Brandon League, Scott Richmond (his autograph is enormous), Mike McCoy, Bill Murphy, Ricky Romero (you can read about getting his autograph right here), Scott Downs, Lyle Overbay, Jesse Litsch, Kevin Millar, Brett Cecil, and Brandon Morrow (who ironically was obtained by the Jays in a trade for the other Brandon on this ball, and came within one out of a no-hitter earlier this season).
As far as potential Hall of Famers? It is still far too early to tell in the careers of many of the pitchers - Romero or Morrow may have a shot - but most of these guys will probably never see the eternal shrine of Cooperstown. But with this particular ball, the enjoyment has been about simply meeting these guys in person long enough to get them to sign their names.