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.
Heartwarming Moments: Asking the Siren trapped in the Gold and Silver misted cave to join you would free her from the enchantment trapping her in the cave and make her the players' friend for life. Heartwarming indeed.
Signature Scene: The Sphere of Annihilation inside the green demon face in the front entrance is perhaps the most iconic trap of the entire dungeon, and that's saying a lot.
That One Level: There are challenges aplenty in the hundreds of other adventures written for the various incarnations of Dungeons & Dragons. This is the one you don't want to see in your game master's hands.
The Woobie: The Siren in the original version of the Tomb of Horrors. Trapped inside the tomb as an personal joke by Acererak. She is cursed so she can't leave the cavern she is trapped in, and neither can she say how to lift the curse, she can only hope the players "Ask her to join them" to lift her curse. Of course, most players would suspect the Siren to be just one of many traps, a shmuck bait or just a monster or simply take one of the bag of holdings resting beside her, resulting in her being erased from existence. On the other hand, saving her would make the players' friend for life.