This Probably Shouldn't Be a Dungeon Checklist

 riffing (badly) from here.

8. a key and a lock

9. a skeleton!
(funny and/or sad)

10. a dungeon self-destruct trigger

11. a vat of goo

12. a potential cave-in prevent you from leaving and turning air into a precious resource

13. a new class you can level up in

14. a message in a carefully boutique conlang of the DM's devising

15. a tunnel to another dungeon

16. letters between the dungeon's master and other major NPCs

17. something like a spell scroll but in a strange medium

18. a statue with gem-like eyes

19. a lifelike statue, spooky coffin, gargoyle, sexy person or other entity that could foreshadow a particular kind of monster (medusa, dracula, gargoyle, etc.) but doesn't in this case

20. vape rig or other wizardly anachronism

21. ducts you can but probably shouldn't crawl through

22. fashionable clothes

23. orcs, done right this time

24. the Devil, looking to make a deal

25. a way to permanently change your primary attributes

26. someone ready to swear vengeance

27. someone who could plausibly be a PC's cousin

28. confidently incorrect plot hook from a map or book

29. one-way travel

30. dope vehicle or mount, and you're actually allowed to use it

31. a way to accidentally fuck it all up

32. mundane animals

33. thematically appropriate painting

34. big ol pile of trash

35. dead adventurers as environmental storytelling

36. obnoxiously trapped chests

37. passwords

38. national anthem for the bad guys

39. rival adventuring party, American

40. shop in the middle of nowhere

41. consumable, multi-dose magic item

42. magic item that has a cost of making you drunk when you use it

43. on a neutral reaction roll, the bad guys need to have a sport or card game they resort to

44. wheedling second-in-command

45. turn all the doors that could be secret doors into secret doors

46. a lever or button with no apparent function that has a radical effect on the dungeon

47. gross smells for all the monsters

48. elfs, done right this time

49. ridiculous over the top overkill trap (with sawblades?)

50. roll twice and combine