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.
Alex Jackson - Moving up to A ball.
2015 Clinton: .129/.227/.188/.415
2014 Peoria: .280/.344/.476/.820
Forrest Snow - Working as a swingman and spot-starter for Tacoma.
2015 AAA: 1-1, 3.86 ERA, 14 K, 1 BB, 0.980 WHIP
2014 AAA/AA: 3-4, 4.01 ERA, 75 K, 25 BB, 1.260 WHIP
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 - Hitting .343/.431/.700/1.131 over two seasons in Korea.
Matt Mangini - Out of baseball. Assistant coach for a high school.
Mike Morse - Won a WS ring hitting .279/.336/.475/.811 for the Giants.
Jamal Strong - Let go after 2005. Played in the Yankees, Cubs and Braves systems.Last seen as a scout for the Cards.