Konosuba, Monogatari Series and Lucky Star.

Anything that relies heavily on familiarity of weeb culture or Japanese history.

FLCL.

And if movies also count "Grave Of the Fireflies".

Eminence in Shadow. If you are not aware of chuunibyou, you'll think it's meant to be taken seriously.

Komi-san. The characters are all exaggerated parodies that will go over their head if they don't know the tropes being lampooned. And also the fact that the show is only good when one particular character is not onscreen, and you have to build up a heavy tolerance to Anime Bullshit to be willing to put up with this stain on an otherwise great show.

Certainly Gintama. Several of the main characters are parodies of actual Japanese historical figures few westerners would recognize, and there are a ton of points where it plays off of everything from other influential anime that non-anime fans might at least be tangentially familiar with (Gundam for example) to classic rakugo stories that they definitely will have never heard of (Jugemu).

Serial experiment lain maybe? Seems like a bit "much" to hand someone new

That parody Fate series. Hell, I've seen a bunch of Fate, and it still didn't make sense to me.

Horizon in the Middle of Nowhere.

Good luck having anyone you show it to to understand what the hell is happening. I don’t know what’s happening, but it constantly dumps more lore and literary references to Japanese and western history & folklore. It’s also very dialogue heavy. And the women are all drawn in a very specific way.

I watched two seasons hoping at some point I’d understand what the hell was going on, but I just got more confused. It apparently makes sense as a light novel? But the anime squeezed way too much into each episode.

Cuck porn

edit.: Strike all that. It's too early, and my reading comprehension wasn't turned on yet. Explains at least why all the recommendations were especially shit.

I consider Anohana: The Flower We Saw That Day the perfect beginner anime for a couple of reasons:

• short - with only 11 episodes it's not a huge time investment (compared to multi-cour shows or mammoths with hundreds or thousands of episodes)
• universal - the concepts of the show are universal to every gender and culture. And you don't need to know or learn any Japan-specific terminology to immediately understand the plot (ie. chuunibyou, shinigami, yokai, etc.).
• everyday people - the show has normal people who are thrown into an uncommon situation, which makes it easy to empathize with the characters.
• likeable characters - self-explanatory.
• believable - the show is juuust outside the norm. Enough to be interesting but not so far-fetched that every little thing is a new concept watchers have to wrap their heads around.
• instant hook - the show's hook is near-instant. No "it gets good after 10 episodes" or "once the X arc starts in episode 180 it's really great".

Steins Gate

• it's a long-burn, might give the wrong impression of it being boring
• it will break their heart

boku no pico

Mushoku Tensei, definitely gonna traumatize them one way or another

Inuyashiki. That isn’t a typo — I’m not talking about the canine ninja dude, I’m talking about the old man and the young man who get replaced with killer androids. That second episode…

I got started on Dragonball, but I don't know if it's recommendable as someone's first anime? On one hand, it's so popular and so influential on so many anime that came after, it helped me familiarise myself with the tropes and stuff, but on the other hand, it's too long and could be intimidating for new people. I guess Detective Conan and One Piece for the same reason. Something that says all it wants to say in about 30 episodes seems like a better first anime.