Fastest Bat Swing - 55.39 m/s
Baseball Bat Weight - 0.94 kg
(1/2*0.94)(55.39^2) = 1441.98 J
Results
Peak Baseball Bat KE - 1441.98 Joules, Street level
Sources
Fastest Swing - http://ftw.usatoday.com/2016/06/giancarlo-stanton-miami-marlins-statcast-fastest-ball-video
Baseball Bat Weight - http://vsbattles.wikia.com/wiki/Baseball_bat