Star Trek

Hard to name three - could easily put a dozen on the list as they are all very close.  Here is my top 3, could change the order

1) Blink of an Eye - I'm a sucker for this episode, the idea of a civilization going from ancient times to the future in the matter of days intrigues me

2) Tinker, Tenor, Doctor, Spy - Love the Doctor, my favorite character in the series

3A) Living Witness - Great episode, negative view of Voyager through the eyes of a planet 700 years in the future.

3B) Muse - As with Blink of an Eye, I love Trek shows (or any show for that matter) that delves into ancient periods like Greek, Roman, etc times.  I'm a romantic for these periods in history.

Close, could easily make the top 3 for me:

Endgame

Message in a Bottle

The 37's

Year of Hell

The Killing Game

Fair Haven

Workforce

Meld

Friendship One,  The 37's,  Scorpion  parts   1 and 2

This is neber easy and I have different moods but I's say...

1. Scorpion

2. Timeless

3. Dark Frontier

On another day, I'd say...

1. Blink Of An Eye

2. Future's End

3. Someone To Watch Over Me

don't remember the names haven't watched it since it was on, but i'd say the one where they guy who lost his wife was messing with time

The one when kes comes back and they destroy the female caretaker

and a tie between one of several of the borg queen episodes, the one with the time correctors and the one with the 29th century borg "mating" of "The Dr." and "7 of 9"