TOS: City on the Edge of Forever: Classic time travel story involving morality.
TAS: (haven't seen it, sorry)
TNG: Yesterday's Enterprise: Again, classic time travel story involving a difficult choice of sending people to their deaths in a hopeless situation in order to bring about a better future. Also gives Yar a better sendoff and has the Enterprise-C.
DS9: Past Tense or Trials and Tribble-ations: Another morality focused episode along with an episode that's a celebration of old trek.
VOY: Relativity or Shattered: Seven has to be stealthy and stop a time plot and a kind of a clip show/bottle episode, but in a fun way. Also has someone explicitly tell Janeway to try to avoid time travel, which she obviously listens to.
ENT: Twilight: I think there's a theme going on in my choices...
DIS: Such Sweet Sorrow, Part 2: Let's Discovery do its own thing and it was better for it.
LD: Crisis Point 2: Paradoxus: There's not much to choose from, so the holodeck will have to do. Pokes fun of the movies, in a nice way.
PIC: Season 2: The entire thing I guess, but not exactly my favorite...
PRO: (not sure): I guess the whole thing is time travel related...
SNW: A Quality of Mercy: Limited choices again but it does pretty well at looking at a classic from a different perspective.
I think my favorite is city on the edge of tomorrow! I have no clue what I would've done in Kirk's position but I don't think I would've been strong enough to let her die even if it changed everything