My 1 pence for you all (about $0.02 given the current Sterling/Dollar exchange rates
)
Original Star Trek
Choice of two for me, the episode where they meet the Romulan warbird bLasting the federation base, or the episode where they meet the funny carpet-like creature which burrows through rock and murders people, but actually is a very nice evil minded murdering varmint
Next Generation
Dunno, any episode that doesnt revolve around Wesley having growing pains, or Ryker/Data/Geordie insert lead character of choice having some personal problems.
Personally, any episode with a high body count
Deep Space Nine
Better show for me, basically any of the Dominion War epsisodes with a high body count were fine with me
Voyager
Hmmmmm, not convinced on this one, but again, any episode with a bit of mayhem was quite entertaining
Enterprise
I quite like this one, if mainly cos the weapons officer is English. And T'pol does help on the eye candy front - basically, any episode where T'Pol wears a tight T shirt, and that Redneck person gets a "whuppin'" (is that how you say it?)