An offhand remark on the boards the other day left me thinking about bad Star Trek episodes. My least favourite episode -- ever -- would have to be "Shades of Gray". It's the final episode in Season 2 of Next Gen and is simply a clip show with a weak thread "holding" it together. There's others not so good but this one is absolutely appalling.
It's funny you mention that; "Peak Performance" was just on Peachtree TV here in Atlanta and I told my wife (who is a big TNG fan) that it would've been a much better season finale than the one they actually used.
TNG Season 2 had some crap in it...
* "The Outrageous Okona" -- Data's a comedian with Joe Piscopo
* "Shades of Grey" -- Talk about a bottle show... everyone just sits in Sickbay
* "Up the Long Ladder" -- Could've been a great commentary on cloning but was weakened by the Irish stereotypes
* That one where Pulaski got older and they solved it with her hairbrush but then why don't they just do that to everyone to make them young forever? She remembered everything that happened on the shuttle, but they reformed her pattern from old DNA? WTF?
* "Pen Pals" -- At least Nikki Cox grew up to be hot enough that she can pretend no one remembers THAT role
* "Samaritan Snare" -- Another good Picard/Wesley episode that was shattered by the Pakleds -- by the way I once watched that episode with, I think, Swedish subtitles... it was HILARIOUS
* "Manhunt" -- the WORST Mrs. Troi episode ever, where she casually solves the mystery at the end... WTF?
It also had some good ones, but that's like 33% of the second season that was horrible. How did the show ever get renewed?
I would have to say that "Manhunt" is my least favorite TNG episode. I also didn't like "Bloodlines", where Daimon Bok returned (late in the series) and brought Picard's "son" with him. That one was pretty lame.
TOS: I know "Space Seed" was a great episode, but it's been in EVERY TOS marathon and I'm so sick of it.
I haven't watched the others enough times to form an opinion, but for Voyager, any episode with the town of Fair Haven instantly went on my crap list. Janeway falling in love with a hologram? Okay, the Doctor became sentient, but the other guy's just a... a toy! You're a damn starship captain! Grow up! Have sex with Chakotay already! The entire audience can smell the sexual tension from 75,000 light years away!