If it's all about length, then put the Toy Cannon on the list. He'd belong there just as much as Allen.
But if the question is "Is there a player who, in his prime, would cause you to drop everything just to watch him take an at bat?" - Gotta say that my preferences will lean towards the guys who were not only sluggers, but great all around hitters.
Pujols, Howard, Mantle, Mays, Griffey, Aaron: these guys were great all around hitters.
Reggie, Strawberry, McGuire, Allen: these guys were all one dimensional sluggers for the most part.
Bonds? Lord knows what he would have been without the chemical assistance.
Forrest Snow - Suspended for the first 50 games of the season. (Come on, Forrest. Just because it's legal in Washington...)
No invite to Spring Training. Not assigned to any team. Contract still owned by the M's, but effectively out of baseball for now.
2013 AAA/AA: 5-5, 2.96 ERA, 84 K, 28 BB, 1.085 WHIP
2012 AAA/AA: 5-9, 6.35 ERA, 99K, 67 BB, 1.674 WHIP
Gone But Not Forgotten (former adopt-a-players):
Eric Thames - took his MLB .250/.296/.431/.727 and MiLB .305/.383/.508/.892 statlines and went to play in Korea.
Matt Mangini - Out of baseball.
Mike Morse - Now playing for the Giants.
Jamal Strong - Let go after 2005. Played in the Yankees, Cubs and Braves systems. Now a regional scout for the Cards.