Fade In to Murder - 1976 - Playing TV's most popular dective who kills his blackmailing producer. Great fun episode where Shatner sends up himself as the egotistical actor.
Butterfly in Shades of Grey - 1993 - Where as a domineering LA radio talk show host he kills a member of his staff to stop his step daughter furthering her career. Shatner really is quite despicable and menacing in this episode when compared to how he played the killer in 1976. One of the better of the 1989 series revival episodes.