Gimmicks that work..only once!

[Joethegoblin]

So I thought of one gimmick to inflict on my players, something basically out of a movie.
Basically a dream sequence, without them realizing it is a dream sequence.
One character (who is a psion) dreams of them getting ambushed in the middle of the night, cue a fight which they all horribly die in, only for said character to wake up, and then later on, not even the same session, the exact situation arises, where said character can avert the horribad death situation.

What other movie/tv gimmicks are performable in an enjoyable manner?
And of course, you can probably only perform it once.

No groundhog day.

Let your imagination run amok!

[Galithar]

The favorite I heard is kind of a "lesson to murderhobos" so it's obviously not appropriate (read: likely won't work on non murderhobos).

You let the party casually discover a tower/keep/mine/dungeon of choice on their travels. In this tower are rather large numbers of weakish humanoids, preferable for most of them to not share a language with anyone in the party (and definitely not with a reasonable character) but a full blown murderhobo party won't need that obstacle. At the end of the dungeon the 'boss' is a perfectly reasonable research wizard that is horrified that you murdered his associates and casts sending to inform the local constabulary of your horrible murders using his first turn of combat. Then teleporting away on the second turn if he's still alive and able. He later returns with the local law enforcement or a lunch mob to arrest the party and/or kill them.

Edit: it's important that this 'dungeon' be described in perfect innocent terms and to not actually give them reason to think things should be killed

[SimonMoon6]

Something I'd like to do sometime when the PCs are dilly-dallying and not getting to the adventure in a timely manner:

As the PCs arrive at the dungeon entrance, something seems different. They notice wagon wheel tracks leading away from the dungeon. The tracks are thick in the mud, suggesting the wagon was carrying something heavy. As the PCs enter the dungeon, they find that it's been cleared out. Not only has every monster been killed, but every trap has been tripped/deactivated and every single piece of treasure has been taken, even the big and bulky items that nobody would reasonably carry away.

Investigating further, the PCs follow the wagon tracks. They catch up with the wagon just as it is barely outside the city walls (so if the PCs try anything violent, the city guards can show up and try to interfere). As it turns out, there is a rival group of adventuring heroes. These heroes have a cool group name (I bet the PCs don't have a cool group name) and they claim to be the best adventurers in the land.

From now on, the PCs have a rival group of adventurers that they have to deal with. If the PCs don't solve a mystery in time, the others guys will. If the PCs don't stop the evil dragon lord in time, the other adventurers will. But the other adventurers aren't always successful. Sometimes they will make things worse. If there's a door to open that will unleash a demonic horde, guess who opens it? If there's a button to push that will free an ancient dracolich, guess who pushes it?

[Name_Here]

Have a NPC named Rotiart. Who absolutely nobody suspected of a single thing.

[Berenger]

Have a NPC named Rotiart. Who absolutely nobody suspected of a single thing.

I had a mercenary team named Benedicta Arnolds, Hagen von Lindenruh, Vidkin Quislund and Judas di'Traittore and the player did not suspect a thing, either.

[CombatBunny]

Having the PCs be under a spell that switches their bodies randomly. Specially if you ask the players to switch their character sheets as well to add to the confusion. The first time it might be fun if the players haven’t been exposed ever to this mechanic, the second time you will have eyes rolling all over the table.

[Spore]

A former DM of mine made an evil drow oneshot for the time where two players could not make it. We did odd random stuff, until one player made a pact with the neutral-ish ally of our actual (heroic) group. He would attack the king and be killed* and the neutralish dragon ally would be praised as a hero.

It was pretty surprising because the actual player inserted himself as a minor villain into the main campaign which was incredibly cool.
__________
* with the villain actually being a vampire.

[Kurald Galain]

Play Paranoia with people unfamiliar with that system, and tell them in advance that one of them is a traitor, just like in numerous cooperative boardgames.

[Tawmis]

My all time favorite was published in an issue of DUNGEON Magazine.

The players got reports of a White Dragon terrorizing the land.

The party obvious prepares to deal with frost type spells and a weak dragon.

Little do they know it's an albino Red Dragon.

Such. An. Amazing. Effing. Twist.

[BWR]

Vidkin Quislund

To be fair I wouldn't expect any non-Norwegians to get this one.

Judas di'Traittore.

There is precious little excuse for not getting this one if you live in a country with a history of Christianity.

My all time favorite was published in an issue of DUNGEON Magazine.

The players got reports of a White Dragon terrorizing the land.

The party obvious prepares to deal with frost type spells and a weak dragon.

Little do they know it's an albino Red Dragon.

Such. An. Amazing. Effing. Twist.

I did something similar, a blue dragon who used illusions to appear as a black dragon. It worked wonders against the party and the look on the Magus' players face when told his intensified shocking grasp critical hit did bugger all was priceless.

[The Glyphstone]

Eh, I got it and I'm not Norwegian - 'quisling' is one of those words that English stole shamelessly for its own use, so it's clear in context.

[Kraynic]

In the novel "Witch World" by Andre Norton (at least I think it was the first book, it has been a long time since I read it), there is a scene where 2 characters are in a below ground ruin. They enter a good size room that they are just passing through, but this room has a raised dais and a throne, with a statue on the throne holding a weapon in it's outstretched hands. In the book, one of the characters recognizes the figure represented by the statue and the weapon held. He takes hold of the weapon, but instead of trying to take it, he speaks to his need for the weapon, his intention to take care of it and use it in a fashion that would make it's previous owner proud. The statue crumbles to dust leaving him holding the weapon.

I have found that if you put this situation in front of adventurers, they would likely never think of asking for the weapon. I don't make it deadly. The passage they entered through and the passage across from it remain open allowing them to leave at any time. Every time they attempt to take the weapon instead of asking for it a batch of adversaries is summoned, with the challenge increasing each time. The summoned adversaries do not block the exits and are content to drive the adventurers from the room. Now, it is totally up to you whether the weapon/item held by the statue is actually of any value in the game, though it is best for "trap value" if it looks like something one of the characters could use. And maybe it actually is!

[TheTeaMustFlow]

I had a mercenary team named Benedicta Arnolds, Hagen von Lindenruh, Vidkin Quislund and Judas di'Traittore and the player did not suspect a thing, either.

Might be having a dumb moment, but who's the second one referencing? Hindenburg?

[Jay R]

I had a mercenary team named Benedicta Arnolds, Hagen von Lindenruh, Vidkin Quislund and Judas di'Traittore and the player did not suspect a thing, either.

You can safely hide any clue in the NPCs' names. Those names will look really obvious on the DM's notes page. But to the PCs, they will be "That Wizard Back In The City", "That Fighter With The Axe", "That Elf Druid We Met In The Forest", and "Oh, Yeah, That Cleric, You Remember Who I Mean".

[Berenger]

Might be having a dumb moment, but who's the second one referencing? Hindenburg?

Hagen von Tronje is the guy that assassinates the hero Siegfried in our national epic, the Nibelungenlied. Lindenruh is a reference to the linden leaf that rested on Siegfrieds shoulder during his bath in dragon blood that rendered him otherwise invulnerable.

[Alhallor]

I always liked the fight on a Train sequence.

Every trip attack is twice as deadly, the adversaries (or the heroes) can try to use spells to get some wagons away, you have to consider Innocents, etc. etc.

But it only works if your world has a fitting equivalent or is in a modern setting.

The other idea what I pulled once or twice is giving them a very obvious riddle and let the most obvious answer be the correct one. (There is a chessboard in the middle of the room, with a burnt corpse on one side. As soon as one of the Players steps up in front of the chess board there are surrounded by a ring of fire that get's closer and closer for every turn they make and they have like 10 turns. Of course somewhere there is writing on the wall that says "only if the other king falls you will survive." And the solution is to just topple the other king over instead of playing the game normally. Works great if you really set down a chess board.)

[The Glyphstone]

I always liked the fight on a Train sequence.

Every trip attack is twice as deadly, the adversaries (or the heroes) can try to use spells to get some wagons away, you have to consider Innocents, etc. etc.

But it only works if your world has a fitting equivalent or is in a modern setting.

The other idea what I pulled once or twice is giving them a very obvious riddle and let the most obvious answer be the correct one. (There is a chessboard in the middle of the room, with a burnt corpse on one side. As soon as one of the Players steps up in front of the chess board there are surrounded by a ring of fire that get's closer and closer for every turn they make and they have like 10 turns. Of course somewhere there is writing on the wall that says "only if the other king falls you will survive." And the solution is to just topple the other king over instead of playing the game normally. Works great if you really set down a chess board.)

Oh, that reminds me of a good one.

The players walk into a room that immediately seals and locks itself, with a very large clock or timer on the wall counting down from 5 or 10 minutes. There are tiny holes in the walls, obvious hinges in the floor, and the ceiling is covered in sharp objects and spikes, with a single exit covered in all sorts of locks and runic inscriptions.

When the timer hits zero, the exit door opens. Use an egg timer or other visual prop for maximum effect.

[Galithar]

Oh, that reminds me of a good one.

The players walk into a room that immediately seals and locks itself, with a very large clock or timer on the wall counting down from 5 or 10 minutes. There are tiny holes in the walls, obvious hinges in the floor, and the ceiling is covered in sharp objects and spikes, with a single exit covered in all sorts of locks and runic inscriptions.

When the timer hits zero, the exit door opens. Use an egg timer or other visual prop for maximum effect.

This is best if there is a button in the center of the room that resets the timer!!

[The Glyphstone]

Oh yeah, forgot that bit. Definitely crucial.

[Alhallor]

I used that exact thing for the riddle after the chess game!