What are some of the coolest/funniest uses you've seen for illusion magic/holograms in a game?

Alright, new questions :

67 people looked at this thread and not one of them had a story about illusion-use in their games; are illusions so difficult to use and rule on that people just avoid them? Are illusions actually boring and unlikely to produce good table stories for some reason?

A friend of mine told me several times a game-play (AD&D) anecdote where a programmed illusion was involved.

So his character entered a crypt where were four coffins. Upon entrance all the coffins opened simultaneously, and from each rose an armored undead, all of them in perfect synchronicity. And so the player's character, a fighter, went to boldly fight these undead. Finally, after many wounds suffered and hit-points lost, he finished the last undead, and took a breath. He thought he had been on the verge of dying, and had been lucky to slay them all instead. So now, as a just reward, had come the time to reap their treasure. However, as he thought so, the four coffins re-opened (despite no efforts were made to close them), and four undead rose from them in perfect synchronicity...

Everyone was afraid to post anything for fear I would enter the thread and say "Cool illusion story, bro!"

-clash

They're pretty boring. Useful, but boring.

There's a DCC adventure where a room in a tower has a permanent illusion that makes it look like there's no floor, just a drop straight down into an extremely deep pit. Of course, there is actually a floor, but it sure slowed my players down.

One of my best gaming sessions as a DM: The PC's are in a clearing in a forest, and hear a huge crashing and thrashing around. Eventually, a green dragon comes crashing into the far side of the clearing. I let slip that, looking past where the dragon just broke thru the treeline, there are no more fallen trees. The party's best role player considered this for a moment, and he knew that detail was supposed to mean something, but couldn't place what it was. The party then succeeds in subduing the dragon, and forcing it to fly them to its lair and given them its treasure trove, which included a suit of apparently magical plate mail.

The fighter thinks he's found the rainbow's end, and immediately strips off his armor to don the new suit. Then, everyone feels a pinprick and falls deeply asleep. The pinpricks were, of course, pixies' sleep darts. The whole thing was an illusion they pixies created as a practical joke on the PC's. The lack of trampled timber was a flaw in the illusion, given as a hint so someone might try to disbelieve. There was no dragon, no treasure, and no magical plate mail. The fighter and the druid were pissed that we had "wasted" the better part of an entire session on this. The other two were ecstatic, and thought it was one of the best sessions we'd ever had.

I GM'd a very entertaining session full of mystery and comedy, most of which was provided by the players themselves intriguing and investigating, most of which ended up being provided by unplanned circumstances generated by the players themselves, one of which was, unknown to any of the other players, secretly casting illusion spells to get the PCs and NPCs to investigate various clues and suspicious sounds...

The interesting thing about illusions is that they work best when they are subtle enough to not be questioned. Sometimes less can be more effective than more. That player and some others could probably get more done with the ability to secretly create a sound at a distance, than with more high-powered (and obvious) magic.

The drawback of illusions, from a fun/fairness/balance perspective, is that unless your game system or setting are very high-powered (or has strong/common illusion counters/nerfs), a determined and clever illusionist can probably do crazy amounts of damage in ways that can seem pretty unfair.

One of my first dungeons after I discovered Labyrinth Lord had a room whose sole purpose was to house an optical/aural illusion of a large pit with awful, dripping, evil tentacles thrashing about wildly and at great speed. The party made multiple treks to carefully mark all the doors leading into the chamber that they could find, so they'd never have to face "the thing in the pit," never once getting close enough to see that they could walk through it into the otherwise-inaccessible passage (and it's treasures) beyond.

I ran AD&D 2E in my younger days, and nobody could ever find a use for the "Nystul's Magic Aura" spell. (For anyone in need of a refresher: the spell places an illusionary aura on a mundane item, making it appear magical.)

One fine day I was prepping for the next adventure, and randomly rolling spells for a dragon the PC's might encounter. (Sure enough, they did, and they kicked its ass.) I rolled Nystul's Magic Aura, and got a classic Evil Dungeon Master idea....

I used encumbrance rules. And the PCs didn't have a bag of holding, portable hole, or other labor saving magic item, so they had a habit of picking the choicest (magical) bits out of large treasure hordes, and leaving the rest because they simply couldn't carry it all. You can see where this is going. Dragons are very long lived, and have daily use of their spells....

So they kill this dragon, and begin examining its truly immense treasure horde, casting Detect Magic as usual, only to find that every single item in it, down to the last copper piece, appears to be a magic item of some sort, and picking out the real magic items was going to be extremely difficult, if not impossible.

All the players turned to me in unison and said "You're a dick."

I love that ^.

In our DCC game, Bill the Elf was probably one of the campaign's most memorable PCs, but interestingly enough he didn't have most of the really hardcore damage-spells.

He made up for this by very creative use of the spells he did have, including Cantrip, which he'd often use in very unexpected ways.  For example, he got rid of a large number of heavily armed drug gangsters ("Los Thetas") by tricking them into shooting at an illusion of one of their hated enemies (Slothy Rodriguez), the shots of course sailing right past the illusion and hitting the explosive device he had rigged right behind the illusion.