Shoeless Joe Jackson (it's hard to believe that he was actively involved in the Black Sox scandal, considering he batted .375 in the series his teammates were throwing), Pete Rose (the career hit record is too big to pass up; he may have bet on baseball games, but I'm sure there are plenty of others in the same era who did it but didn't get caught), Lefty O'Doul (.349 career batting average is highest among players not eligible for the HOF; he didn't play the 10-year minimum to make it to the hall), possibly Albert Belle (posted the best overall offensive numbers of the '90s and only retired because of injuries; sure he was real surly and unpleasant to be around, but Ted Williams acted very similar for most of his career)
"Today, I consider myself the luckiest man on the face of the earth." -Lou Gehrig