dare-to-dm:

For when you want some variety for your tabletop RPG.  These events will also give your players a chance to use character skills they don’t often have opportunities for.

• Natural Disaster – Have the town the PCs are in catch on fire and see what they do!  Do they cut their losses and run?  Do they heroically try to save trapped townspeople?  What do they do about the aftermath?  Natural disasters are an interesting challenge because there can be lots of danger and drama without necessarily having a villain.  It may also get your PCs to use skills they don’t commonly have a chance to.  You could also try floods, earthquakes, raging storms while at sea, etc.
• Powerful Fortress – Put one of your party’s goals in a location where they won’t be able to prevail through combat alone (Example: a fortress where they are vastly outnumbered).  Your players will have to rely on either stealth or guile (or both) to accomplish their goal.  The pacing of such events can be frustrating to some players, but few sessions are as rewarding as a creatively executed heist or infiltration.
• Dangerous Crossing – Give them a dangerous physical obstacle to overcome.  A canyon, or a raging river, or quicksand or an old battleground littered with traps and mines.
• Festival – Have the PCs encounter a festival or tournament!  With lots of contests! This could be a good opportunity for them to build their fame and fortune (especially if you allow gambling).  Some of my favorite sessions have involved festivals.
• Entertainment – Put the PCs in a situation where they have to entertain someone.  What do they come up with?
• Letter – Have one of the PCs receive a letter, either from an NPC they’ve dealt with before or from someone involved with their backstory.  This is a good way to make the consequences of their actions seem more real.  You can also use it to introduce new plotlines/sidequests.
• Crafting Challenge – Put the PCs in a situation where they need to craft something in order to accomplish their goal.  Maybe they need to make something in order to fix a mechanism?  Or in order to satisfy some local gift-giving custom?  Or they need a forgery?  Maybe as part of an exchange for something else they need?
• Lost and Found – Have your PCs discover someone or something that is clearly lost.  Maybe they find an infant in the wilderness.  Or a key with a strange inscription, or some kind of talisman.  Throw in a clue or two to present your players with a tantalizing mystery.  
• Inhospitable Wilderness – Have the PCs go somewhere it’s an effort just to survive.  A barren desert, a treacherous swamp with poison gasses, a forest so dense the ground never sees the sun, or even the bottom of the ocean.  Test their endurance and survival skills!
• Dinner Party – Have the PCs be summoned to a formal event!  Test them on the battlegrounds of social grace and etiquette!  Even better if it’s in a dangerous environment or an alien culture.
• Thief – Have something important stolen from the PCs.  See how they handle it.
• Needle in a Haystack – Give the PCs something very difficult to find.  Like a single specific housecat in a sprawling metropolis, or a legendary weapon of which there are many fakes/copies.  

Really, if you need any more inspiration, look at your player’s character sheets and see if they’ve invested any points in a skill they haven’t gotten to use much.  Then invent a challenge they could feasibly use that skill for.  If you can’t think of a situation that could be helped by an Appraise, Craft: Calligraphy or Handle Animal check, you need to practice your own creative problem solving skills!