Justice League Unlimited Episode: Task Force X

Four convicts are released by Cadmus to steal a mystic weapon the Annihilator (first appeared in the episode  Hawk and Dove)  from the Justice League in the Watchtower.

Guests
 Michael Rosenbaum (Deadshot/Floyd Lawton)  Of course Rosenbaum is also the Flash and Smallville's Lex Luthor.
Adam Baldwin (Colonel Rick Flagg) also did the voice of Jonah Hex in the episode Weird Western Tales. He appeared on the X-files as well.
Juliet Landau (Plastique/Bette Sans Souci)
 Donal Gibson (Captain Boomerang/George Harkness)
 Alan Rachins (Clock King/Temple Fugate) 

This episode features the Shining Knight, Vigilante, and Atom-Smasher along with some of the regulars.
These three heroes were originally Earth 2 heroes before the Crisis on Infinite Earths. The Shining Knight and Vigilante were part of a group known as the Seven Soldiers of Victory. 

The Shining Knight became a member of the All Star Squadron in the 1940's. He's been back and forth in his original time period summoned by Merlin to today's time period. His first appearance is Adventure Comics #66 in September 1941

The Atom-Smasher made his debut in All-Star Squadron #25 as Nuklon a member of Infinity Inc. He's the guy with the Mr. T hair cut. 

First Appearance of Atom-Smasher in All-Star Squadron #25

Al Rothstein is the grandson of the villain known as Cyclotron. He chose to follow the steps of his godfather, the golden age Atom, rather than those of his grandad and became a hero. As Nuklon, he joined Infinity Inc.

The Vigilante made his first appearance in Action Comics #42 (November, 1941) was a member of the Seven Soldiers of Victory and got his own movie serial in 1947.

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