Just finished TOS. Here is my "best and worst episodes" list.

Would be interested in hearing yours.

I try to not look for community opinions until after I've seen an episode, as to avoid becoming influenced by other people. I did the same with TNG and it seems like I mostly enjoy what others enjoy. Some interference is unavoidable but it is all just in good fun.

Overall there are very few episodes I would consider outright bad.

Favourites

Season 1:
Miri
Balance of terror
City on the edge of tomorrow

Season 2
The deadly years
A private little war

Season 3
Plato's stepchildren
The Empath

Least favourites
The omega glory
And the children shall lead