My favorite episode of ST:TOS -- the Doomsday Machine. I love the guy who plays Matt Decker, he is such a convincing lunatic. Very heavy handed overacting, but that's part of what's great about Trek, right?
It's sad that so many of the old Star Trek actors have passed away. That was such a wonderful show, and left such a terrific legacy. It's really a shame that after the Great Bird died, the franchise was just milked to death and has now basically collapsed.
I miss Star Trek :(