Shirtless Kirk fighting the 3 other drill thralls in The GAMESTERS of TRISKELLION: one of the longest extended fight scenes, with the funniest rules of battle (watch as Kirk repeatedly steps on the wrong coloured tiles but still doesn't get penalized). Great choreography...Shatner at his best!
It's tied with the end battle in A PRIVATE LITTLE WAR: high drama as Tyree's wife plays both sides against her husband's tribe, is ravaged and quickly killed as Kirk and Tyree appear. A vicious fight ensues, ending with the look of despair on Tyree's face after he mercilessly pulps his enemy's face. Bonus points as Kirk is completely overwhelmed at how seriously his interference has f'ed up his longtime friend's life... No easy solution this time for J.T.