I couldn't narrow it down to only 10. I was left with 15. These 15 episodes of Star Trek are on my DO NOT WATCH list.
My List in order of appearance, not rank:
-Mudd's Women - Not horrible , has a couple fun elements, and the questioning of mudd is cool, but the corny end makes it unwatchable for me.
-Miri - Hodgkin's retarded law of parallel planet theory bullshit is retarded bullshit. Can't stand the children actors in this, even the "good" ones.
-The Alternative Factor - This episode will give you an Aneurysm. Stay away.
-Catspaw - I like beginning until we meet the main villains and then it's really, really boring. The funny puppets at the end are worth a look.
-Friday's Child- This episode just sucks. Dr. Mccoy hits a pregnant lady though, that was funny.
-I, Mudd - This episode has really embarassing scenes. It's just very dated and lame feeling.
-A Private Little War - Stupid Viet Nam war 60s propaganda.
-A Piece of the Action - I've never been able to sit through the whole thing. It doesn't work as a comedy the way Trouble with Tribbles worked. I guess I just don't dig the whole 20's mob thing. Just seems like a cheap money saving decision, except without the creativity or subtlety normally used in making such decisions.
Spock's Brain - Dumb
-And the Children shall Lead - This episode is bad, but it isn't as bad as it's made out to be. But it's pretty meh. I actually enjoy it more than most, but it's pretty universally hated. I usually hate episodes with lots of child actors though.
-The Empath - Gem the empath is annoying and stupid looking. This episode has some nice concepts, but fails in most of it's execution. Very boring to sit through.
- That Which Survives - Not as bad as people say, but still cheap, stupid, and lazy.
-The Mark of Gideon - Ridiculous concept and solution.
-The Way To Eden - Cheesy and hard to sit through. More embarassing musical scenes.
As for the worst episode.....
Assignment: Earth -This doesn't even qualify as a Star Trek Episode and therefore automatically must be the worst episode of Star Trek ever. It might be entertaining TV, but it isn't Star Trek. It's Gary 7. Kirk and Spock make a cameo appearance.