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.
Narm Charm: Simoun has a bombastic, frankly ridiculous, and at the same time entirely appropriate climax: the Heel-Faith Turn of the Plumbish nation. It is so great partly because it is so overblown and melodramatic. See the concept of 'eucatastrophe' (first described by J. R. R. Tolkien) for more on this.
Nightmare Fuel: In the second episode, after visiting the Spring for her gender assignment, one of the former Sibyllae of Chor Tempest leaves with this devastated look on her face. She starts to cry, and then collapses amid screaming tears. Since she still couldn't make up her mind after entering the spring, it chose for her.
Subbing versus Dubbing: Actually, more of a Subbing Versus Other Subbing. With a two year delay between its airing in Japan and its DVD release in North America (Although incredibly fast when compared to some other Anime) there was already a fansub circulating on-line (and a few episodes' worth of a second) before an official version was presented. None differ from the others in any significant ways, but neither can any agree on the proper ways to spell the characters names, and there are many different ways to "really" translate certain sentences.