Random items, stats, and attribute changes tied to certain character names.

Name your character after certain dictators and you spawn with high Charisma but crappy Int
Name yourself Homer Simpson and spawn with crappy Int, ton of bottles of Vodka and better Arm Strength.
Name yourself Harry Potter and have lower Endurance but higher Mana.

Oh, the FUN we could have with this one! Shoutout City!

34. Charm every single non-immune person in Attnam and lead them to safety before betraying Petrus. Take over as new high priest with zero collateral damage and dispose of any corpses/body parts out in the wilderness before you sit on the throne.

I did this on vanilla back in 0.50 on my Windows 98se computer. Good times.

How about a keyword - ie; "a fir chest with a curious triangular lock"

Nope. You open it and take your chances. Might need a dedicated disarm key for this.

Oh , we need some kind of Corona reference in 0.59, no doubt.

Outright killing the player "of a rare Asian virus" would be the easiest, or we could make a whole new disease. Coughing sound effect, chest/head damage, occasional unconsciousness...

How about "bat soup" as a material type and the player refusing to drink it with a message like "you hesistate, recalling tales of a ravaged land far across the sea." Naturally it should belong to Scabies...

EDIT: Also, bottomless pits.

Treated as an unwalkable tile like ocean. Get knocked backwards into one, or have your Levitation run out while floating over it, and " (Player) fell into an endless void".

EDIT 2: "Booby trapped" chests.
On an unsuccessful Dex check (Luck save to avoid?) player is hit for damage. Successful check means the chest is opened as usual, and a dagger is guaranteed to be found within. For extra Fun, make it a chance of a poisoned dagger.

On that note, how about flooding?

Make bodies of water not just an obstacle but an actual hazard?

Wife #5, who is supposed to be unable to speak, says "I thank you for your little gift" like all the other wives in Petrus' harem when given a gift.

I love it.

Have a "cloud of noxious fumes" genned on every single walkable square. One spark and the resulting explosion sends you on the Afterlife Express

Maybe if you mine or otherwise destroy a wall, it should get replaced with more cloud to prevent twinking around? Or should a clever player be allowed to dig around the hazard?

I abused half a dozen wands of teleport to get a meteoric steel chest to a dungeon vendor while Overloaded! and sell it for an obscene amount of money. Sadly after all these years that's the first time the idea has ever occurred to me.