"Good artists borrow, great artists steal."

Coming up with something completely new is great when it works, but very often you can create something just as good by taking an idea from somewhere else and making your own version of it.

"The Automatic Hound" from Dungeon 148: There's a lot of things I don't like about this adventure and I wouldn't call it great, but the basic idea is a really good one I am going to use in my next game. Two brothers went exploring an ancient stone circle in the forest and accidentally disturbed a guardian beast that killed one of them before the other managed to slay it. Returning the corpse back home, the guardian arrived in the village later that night, circling the house of the brothers family. When the guardian is slain, the remains vanish after a few hours and reform back at the stone circle at every sunset and the guardian will resume its attack of the house. It's not actually after the surviving brother, but wants the corpse back, as the killing of a living creature in the stone circle is the first part of an ancient ritual. The guardian would try to get into the house, but the rites to prepare the corpse for the funeral also created a ward against spirits on the home.
The PCs will probably attempt to just slay the guardian, which turns out to be futile. Then they need to get the full story from the surviving brother and after that go exploring the stone circle some more. The chambers under the hill hold stone carvings that show the steps of the sacrifice. Next they need to retrieve the corpse, but the family might not be too thrilled about cutting out the heart in an ancient shrine and sacrificing it to an evil spirit. (There might be a chance the PCs will think they need to sacrifice the surviving brother as well, which would be hilarious.) Once they got the body by whatever means, they have to get it to the stone circle, cut out the heart, and present it to the guardian who devours it. The surrounding land will have bountiful harvests for the next year and the guardian stop attacking the village. The original adventure includes the sacrifice ending with a portal to the spritworld being opened for a few hours, which lures another beast to attack the PCs, but that seems to obviously a tacked on boss fight for an adventure that otherwise doesn't really have one, so I probably replace it with some other big action scene.

"Mellorn Hospitality" from Dungeon 107: A village deep in the forest holds a big market every year that attracts many traders from distant places. However, the village has the dirty secret that a nearby cave opens to the underworld every seven year to spew forth horrors that go hunting for captives to drag back home with them. The villagers know how to avoid the monsters, but they won't return to the underworld until they captured a couple of victims. For that reason the villagers started the anual market to provide some easy prey, and since the monsters only come every seven years, nobody notices the pattern of traders occasionally going missing.
The PCs arrive at the market, possibly as guards for a trader, in one of the years when the monsters attack.

"Species 37" from Mass Effect: (spoiler for Mass Effect, obviously) One of the main story levels from a sci-fi videogame, I think it's just brilliant for a Sword & Sorcery adventure and I'm totally going to run this once my players have three or four adventures under their belt with their current characters.
A small village lies in the ruins of an ancient city, which actually happens to have a very large underground complex below it. A sorcerer arrives with his unhuman minions (snakemen, fishmen, grimlocks, or the like), because he knows of an ancient creature of great intelligence sleeping in the underground halls and wants to force it to reveal its arcane secrets. His minions attack the village to look for an entrance into the underground ruins, causing for a messenger to be send out for help.
Eventually the sorcerers finds and awakens the creature, but keeps it magically bound to interrogate it. However, the creature uses its mental powers to subtly charm the villagers and goad them into trying to come to its help and free it. The sorcerer and his minions become aware of the villagers causing trouble and resume their attacks on the village.
When the PCs arrive, the village is basically under siege by the sorcerers minions and the villagers are acting somewhat strangely towards the PCs. They descend into the dungeons, fighting underground monsters and the minions, until they eventually find the prision of the creature.
And this is were it gets interesting (and diverges from the original source). Both the sorcerer and the creature could try to get the PCs on their side to help them, or the PCs might have to fight against both forces at the same time.