This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Rammstein
The lyrics to the song "Stein um Stein", which describe the process of building someone into a wall. While they're still alive. See for yourself here.
"Mein Teil" also deserves a mention. Partly because it's about the real-life case of Armin Meiwes — indeed, the lyrics are preceded by Meiwes' ad for a young man to be "slaughtered and then consumed" — and partly because in the middle eight, there's a noise in the background that sounds like dying screams. As if the fact it's an eerie metal song about cannibalism sung in a foreign language creepily weren't enough, read the story behind the song in excruciating detail. Yes, he really did that to his you-know-what (hence the title, 'Mein Teil', which means 'my part' in German). And if you're still not convinced as to how frightening the song is, watch the music video.Sweet dreams...
The stage show isn't any less disturbing. Till dresses up as an Evil Chef, with what looks like fresh blood running down his shoulders, smeared across his mouth, and spattered along his clothes. He shimmers, like he's covered in some mixture of sweat and grease, spends much of the song sharpening a knife with a steel and routinely grins and licks his lips at the crowd.
The song also goes on shortly after the lyrics and guitar stop. This part of the song consists of nothing but creepy wailing.
It's also told from the perspective of the guy being eaten. One set of lyrics describes how difficult it is to eat. Why? Because the blood loss is so severe that he can barely stay conscious.
Rammstein generally have either lyrics about sex or murder or both. There are two songs about plane crashes, one about an insane man shagging his decaying dead wife, "Wo Bist du?" (Where are you?) about a man searching for someone in order to knife them. "Ich Tu Dir Weh", so bad that the German government has put it and the album on which it appears, Liebe ist für alle da, on the Index. This means it cannot be sold to minors. (to be fair, the artwork shows them killing and eating women.) And "Haifisch" (Shark) is based on the chorus of "Die Moritat von Mackier Messer" (The Ballad of Mack the Knife).
The masks in the "Du Hast" music video are nothing short of Uncanny Valley.
The cover art of Mutter.
The weird kitchen-object face masks on the Sehnsucht cover.
"Donaukinder", based off Baia Mare cyanide spill, is also scary — both the lyrics and the music itself (with its use of extremely heavy guitars and Ethereal Choir), as typical for Rammstein.
Worse, the first phrase of the chorus translates to "Where are the children?" The singer is watching his hometown die in front of him because of a chemical spill, smelling the rotten fish and birds in the river, and it hits him-Where are my kids?
Add to that by reading up on the disaster- some call it the largest natural disaster since Chernobyl. By the time it got to the Danube (which features in the song title), the cyanide already went through at least 3 rivers big and small, and was highly diluted. The effects were felt not only in Romania, where the spill happened, but Hungary (thanks to the spill almost directly getting into 2 of Hungary's major rivers, first the Szamos then the Tisza), Serbia (via the Tisza and Danube as far as Belgrad), and even as far as Bulgaria. As for the question, the accident happened in January so no children were actually swimming in the rivers, per se, bu they could have been walking along them, and parents from all these places asked that question when seeing fish and other animals die and smelling their rivers stink- and just as the song states, the Romanian government and the mine itself denied everything and claimed ignorance for a good while. "Nobody saw what happened" indeed.
The piano version of "Mein Herz Brennt". The original song is creepy enough as it is (especially the music video for it), but just playing it with only a lone piano is just disturbing. Till's appearance in the video doesn't help matters either.
Towards the end of "Das Alte Leid", a song about the complete pointlessness of the whole cycle of birth-life-death because it only gives rise to yet more suffering, as the band keeps repeating the chorus, you can hear deep in the mix the sound of a baby crying. It goes on. And on.
"Engel". It's a song about how, if you're good, you'll rise to Heaven and become an angel... and then you get to spend the rest of eternity cold and alone, with no way out. The stage version involves a flaming cage.