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.
YMMV: The Decemberists
Accidental Innuendo: May or may not actually be accidental, but in "Culling of the Fold": "Get him down on his knees/ With your hands all shakin'/ That'll teach him how to take it"?
"This Is Why We Fight" Just listen But pretty much anything off that album (or any album for that matter).
Complete Monster: The eponymous character of "The Rake's Song" relates how he murders his three children after their mother died in childbirth because he wants a new life, including beating his son to death and burning the body for daring to fight back, and concludes by saying that he doesn't regret it at all.
Ear Worm: Many, but 16 Military Wives is probably their catchiest.
Every song on The King Is Dead. "Don't Carry It All," "Rox In The Box," "January Hymn," and "Down By The Water" might be the worst.
Genius Bonus: So much of it. For instance, only someone who is both a botanist and a World War II buff would be able to really understand "When the War Came" without being told about it. "Sons and Daughters" references houses of aluminum and eating cinnamon, a pretty bizarre image unless you know that aluminum was once considered a metal more precious than gold, and cinnamon was used as currency.
"The Bachelor and the Bride" requires a working knowledge of Dada art, specifically Marcel Duchamp.
Nightmare Fuel: "Shankill Butchers", "Culling of the Fold", "Odalisque", "The Rake's Song", "The Hazards of Love 3 (Revenge!)", "Leslie Anne Levine", "A Cautionary Song".
Squick: Some of the gory bits, especially the rape scenes.
The Woobie: Quite a lot of their characters. Poor Eli.