When someone reveals details about surprising events which will happen in a movie or book to someone who doesn't know about them, we nowadays say that's a 'spoiler.' I'm looking for a verb for that, which is less colloquial and less awkward than 'to spoil.' Ideally, it would be a transitive verb, so I'd like to be able to say 'He Xed Y,' where 'X' is the verb I'm looking for and 'Y' would be the thing that was revealed.
Before spoiler, people would actually use the word reveal.
Whilst being a verb. it can also be used as a noun, as in the big reveal, such as with a magic show.
verb make (previously unknown or secret information) known to others.
noun (in a film or television programme) a final revelation of information that has previously been kept from the characters or viewers.
Alternatively, you could use unveil
verb show or announce publicly for the first time.
Definitions from Oxford Dictionary
Both work in the context that you've described:
He revealed an object
He unveiled an object
I like divulge:
Make known (private or sensitive information):
Disclose might work well in a formal context:
1 Make (secret or new information) known:
On the colloquial scale, I would rate leak somewhere between spoil and disclose:
2.1 [WITH OBJECT] Intentionally disclose (secret information):
For me, the biggest problem with trying to use “to spoil” as a verb for “reveal” is not its colloquial nature but "the fact" (as seen by me) that spoil/spoiler still really means “ruin” in this sense and not “reveal”:
“Don’t spoil/ruin it (the movie/the ending/whatever) for me [by revealing it (the plot twists/the ending/whatever).”
Granted, the “by revealing [whatever]” can be implied, but it’s not inherent in the word “spoil,” even as it relates to movies, for one can easily spoil a movie in other ways: by talking, farting, checking a phone, etc.).
All that said in a feeble attempt to try to persuade you to reconsider the possibility of using a colloquialism, especially one that does mean “reveal” in this sense and one that could also provide some (clever?/lame?) alliteration when used with “spoil,” to wit,
“to spill”: (6. Informal. to divulge, disclose, or tell: “Don't spill the secret.”).
“You spilled the surprise [ending], you spoiler!”