These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Dark Mercury is also called "Darkury" by fans. A lesser-used name for her civilian form is "Akumi", combining the word for "evil" (whose kanji may be read "aku") and Ami. Rumor has it this name was coined by the show's staff
Fashion-Victim Villain: The Shittenou, because their uniforms in the manga and anime were rather drab. But especially Beryl and Mio in the special act.
Foe Yay / Ho Yay: and how! As opposed to the original anime/manga, Kunzite and Zoisite are at each other's throats in terms of their motives throughout the series. While Zoisite realizes early in the series that his true master is Endymion and continues to protect him from then on, Kunzite wishes to destroy Endymion and Princess Serenity alike for falling in love and leading to the destruction of their worlds. Needless to say, their conflicting motives cause sparks to fly, and Kunzite goes so far as to shove Zoisite into his piano with his sword to keep him down to make a point not to cross him.
Although some of it could be Shipping Goggles due to them being a canon couple in the anime (where they were quite loving and respectful of one another, there was no Foe Yay).
Zoisite and Minako have a temporary cease-fire and even work together in order to keep Usagi and Mamoru away from each other, because they know it can bring about the end of the world.
Zoisite's extreme devotion to Mamoru - much more so than any of the other Shittennou, even after they all regain their memories - certain suggests something on the Ho Yay front.
There's also a little bit of Zoisite/Jadeite Foe Yay near the end of the series due to Jadeite staying loyal to Queen Beryl.
Fridge Brilliance: When the girls are reading Minako's final letter, the camera shows each of them sobbing-Except for Ami, who is crying but not nearly as hard as the rest. At first you think maybe the actress just couldn't pull it off, but then you realize that Ami wouldn't be crying as hard since she wasn't as close to Minako as the other three were; she was the only one who didn't get any special bonding moments with her throughout the whole series.
Fridge Horror: After everyone (especially Rei) insists that Minako should undergo surgery for her terminal illness, she dies — probably from the surgery.
To be fair, terminal illness implies certain death anyways, the surgery at least had a CHANCE of saving her.
Growing the Beard: When attempting to introduce new people to the show, most fans find themselves insisting "It really does get better after the first five episodes!" Episode 6 is generally considered to be about the time when the show finds its groove and the overarching story starts to take off. YMMV, though: some like it right from the start, others find they really start taking it seriously about halfway through the series, when the show gets noticeably darker. Still others find them preferring the lighter tone of the earlier episodes, stating that the darker tone clashes with the show's budget. It's kind of a divisive issue.
Hilarious in Hindsight: The team-ups in the Reiko-Minako battle. For Reiko's team (Rei, Makoto, Ami), their actresses are still in the line of acting in their post-PGSM careers. For Minako's team (Minako, Usagi, Luna), their actresses post-PGSM are on the modeling side, especially the gravure idol genre.
Les Yay: This is Sailor Moon after all, there is a lot of deep, deep girl-girl friendship. The subtext fans go crazy with this show. Even the cast jokes how in love Ami is with Usagi. Rei and Minako's love/hate rivalry/friendship also count. Lots of feelings there.
It even carries over the cast in real life post-PGSM. Considering the relationship of Mars & Venus in Roman Mythology, Keiko (Mars) and Ayaka (Venus) are very close to each other. Mew (Jupiter) and Chisaki (Ami) are also close friends after the show.
Narm: It's hard to take some of the otherwise dramatic scenes seriously when the reaction shots include a stuffed cat with a glittery tear-shaped sticker affixed to his cheek.
The end of Episode 24 is either the most awesome dramatic scene to date, or really stretching the Suspension of Disbelief because of the way the actors are attempting to portray serious injuries (limping badly and grabbing one arm, respectively). It might have worked better if they hadn't dragged out the same limping run for like two whole minutes.
Anything involving Mamoru's anguished or angry face.
Special Effects Failure: At the start (after episode one, of course), the effects (particularly in the transformation sequences) were awful. The team refined their craft over the course of the show's run, though.
Tear Jerker: Anytime a character dies. Except for Manipulative Bitch Mio, which is ironic since she's a clone of Beryl, and Beryl DOES get a sad send-off. I suppose Mio just took Beryl's evil Up to Eleven.
Special mention must go to Minako, who doesn't even die in battle. No matter what you thought of her character in this series and despite the Narm of Artemis' shot mentioned above, there's no denying it's devastatingly sad.