The Campaign Builder's Guild

#20 - Honey I Shrunk the PCs

The PCs get shrunk and must fight their way off of a flea-ridden cat.

#21 - The interbody highway
Two PCs get body swapped, hilarity ensues. +5 points if they're different sexes, +50 points if they're different species.

#22 - Might I interject good sir DM?
The players submit a list of random encounters that they have created. They consist of a name and a short paragraph description of the event. During gameplay the DM randomly rolls dice, if they hit an appropriate number they must stop and roll on the list of player submitted ideas. Everyone must then roleplay through the encounter no matter how serious or ridiculous it is (the DM is free to edit out things like players gaining random powers or other things not in the spirit of what this is supposed to be... a chance to put your rp skills to the test).

#23 - Round robin DMing
This requires people that are comfortable as both players and DMs and can think on their feet decently well. The group creates a bunch of fluff only characters and starts an RP session. They roll a die (or do something else) to determine a set number of minutes that the DM gets to DM. After that time limit everyone passes their sheets one person to the left and continues in their new roles. The only main rule is that there can be no preparation, events and anything else must be thought up on the spot (though everyone is welcome and encouraged to take notes), conflict is resolved by rolling a d20 (highest roll wins, tie = reroll). It makes for a fast paced game where each DM has to be quick to keep things flowing and every player has to be able to keep in character as their assigned personality changes over and over. Voting for best dm, best player, and funnest encounter (etc) afterwards is encouraged.

#24 - Quest beyond the veil
The PC(s) dies and goes to the afterlife only to discover the horrible truth. The "great one" was actually slain many ages ago by his nemesis. This dark god has been maintaining a facade that his foe is still well and looking after his followers so that he can prepare for sudden Armageddon and finally achieve total rule over the cosmos. The hero must make a mighty journey to find a way to return to the land of the living to warn everyone and perhaps stave off the end of the world. All along the way he is hampered by the dark one who has so far succeeded in keeping anyone from returning to announce his plans. Even if they succeed it will be quite a task to defeat him and his forces.

#25 - Shedding the Mortal Coil
A variation of #24, this campaign also takes place in the world of the dead; only the place is unlike anything dreamt up by religion. A strange dreamlike place watched over by enigmatic creatures, this is also the home of anyone who ever lived; ride the soul-winds to the City of Bones, duel with Napoleon over the treasures of the Gatekeeper, and see the post-mortem works of such visionaries as Da Vinci and Tesla. The players take the roles of either newly arrived, the exotic natives, or any of a plethora of dead persons who live on in the strange world beyond our own.

#26 - Orpheus' Descent
In the tradition of the previous two ideas - a single-player campaign in which the hero must enter the underworld to rescue the soul of a lost love/other important person.  Along the way he must overcome various guardians and befriend dead souls or spirits.  The world would be a mixture of the Greek Underworld, Dante's Hell, and Diablo; there'd probably be a heavy sword & sorcery sort of feel.

I'm getting a very big afterlife vibe from these last few ideas hehe...

Actually I have always felt that when you are talking classic fantasy death shouldn't necessarily be the end. Instead of the player having to create a new character (or on the flip side the party just easily raising them from the dead) have them go on a quest of sorts to come back to the land of the living. The afterlife gives plenty of opportunities to explore a new and strange world.

#27 - Suddenly mages, thousands of them!
A sudden cataclysm kills off 90% of the human population. Of the remainer 1% suddenly begin developing strange mystic powers (control over the elements, mind reading, flight, etc). A powerful sorcerer rises from among the empowered, collecting like minded individuals to his cause and forges a coalition of mystics. His quick thinking leaves him in control of the known world as the mystics under him exploit and abuse the mundane population, driving them into a life of slavery and hard labor. Those mystics who resisted are killed or otherwise taken out of the picture. It's 10 years later with the earth firmly in the hands of the Coalition. The players have just joined a group of freedom fighters who have been struggling without success the entire time to overthrow their oppressors. (optional idea: You roll a die for each player, on a certain roll they get marked as a mystic. At some point in the game they will begin discovering their powers)

Why did you decide to kill 90% off for #27?

#28 - Chaos
One day, everyone on earth wakes up with the one power they most want, whether it be flight, teleportation, a shield, etc. None of them are terribly powerful, but the resulting chaos will prove to be an annoyance to the Police force (the PCs) in the cities, who are having to deal with their own newfound abilities...

#29 - Desertion
The PCs awake and find that they have been left behind. Over the night, everyone in the city/region/country/world have up and adisappeared, leaving you the only six people left. Find a way to bring the others back, follow them, see what happens.

Quote from: Cataclysmic CrowWhy did you decide to kill 90% off for #27?

Makes it much easier to have a destabilized world when there are no standing militaries or governments to oppose such a group.

To continue with the superpowers theme:
#30 - The Gifts
People all over the world suddenly discover that they possess strange and supernatural powers. No two of them are alike, although the powers do reappear when the carrier passes away. Most powers are minor: maybe you can bend your bones, make liquids viscous, or remove your eyes without visual impairment. The most powerful abilities - powers of immortality, disintegration, temporal control, prophecy etc. - are guarded both by states and individuals are as much curses as gifts since the carriers become hunted prey. The game could either center around the most powerful of the gifted and their involvement in world politics, or a around a group of gifted losers with less than useful powers.

#31 - The Objects
In 1973 three-hundred-and-seventy-three household items in the small village of Excellence turned magical. All the objects are indestructible and possess different strange powers which rarely have any connection to the original use of the item. From the phone that can eavesdrop on random conversations, over the explosive grandfather clock, to the butterknife that can petrify glass, each item can prove useful in the right situation and are hunted relentlessly by the few who know of them. Players are either thrown into the action when they discover one of the objects, or they came into the game willingly consumed by greed. (this is heavily inspired by The Lost Room - you should watch it if you haven't)

omg #31 is a brilliant idea CC :D

Can I use #30 for the basis of a short story?

#31 really is a great idea; I'm sad I didn't come up with it first ^^ But you should definitely watch the show, or at least check out their list of objects (although most are listed as power unknown because it is a question of trial and error).
And Sarisa, feel free to use #30. It's hardly a particularly unique idea, being but a spin on the classical superheroes idea, excepting the part where each power only appears once (and that many of the powers are less than useful).  

ok this one was just too awesome to not save...

#32 - Would you like fries with that?
The nefarious Burger King kidnaps Princess Wendy and takes her to his White Castle. A Jester named Ronald teams up with a thief who only goes by the name 'Hamburglar'. Along the way, the duo team up with a Purple being, Grimace, a Chihuahua and a retired Colonel. Burger King sends his army of evil red robins to stop the unlikely heroes. it is a quest against time as each group seeks the taco bell... an artifact that could tip the balance of power in favor of the owner.