First thing I ran was a dungeon/adventure I designed myself.
The backsotroy was that an evil party had discovered that the crown jewels of a fallen dwarvish clan were in a certain dungeon. But the monster guarding them was too tough for them. So they established a village on top of the dungeon: the fighter built a keep, the wizard a shop of magical supplies potions &c., the cleric a temple, and the thief a pawnshop and adventurers' store. And they started charging an entry fee for the dungeon and a commission on treasure brought out. They also provided rations for the lesser monsters.
Many years later the PCs, a bunch offirst-levellers on their first adventure, went in just a day after a much tougher party. The party that went in ahead of them were all dead, but the big bad monster (a giant slug, if I recall correctly) was on it last legs too. So the PCs got to put the fatal blows on a monster much tougher than they could possibly have taken normally. Then they decided to smuggle the dwarvish crown jewels out of the dungeon, not paying the commission (a good idea--the eveil party who ran the village intended to pinch the dwarvish crown jewels from whomever brought them out). And they got away with that, but they took the stuff to the pawnshop to have it valued.
A little later the party hit off across country with most of their loot, pursued by a much tougher party, the town guard, and some of the monsters out of the dungeon. If they had stuck with it they would have come to a Dwarvish military road (it ws marked on their map), and there they would have encountered a dwarvish military detachment that would have saved them from their pursuers--but siezed the dwarvish cultural treasures, and left the PCs with only a reasonable amount of loot for their first level.
It would have made a good story in the Leiber vein. But as a D&D adventure it was a flop. Before the characters got to the dwarvish road the players told me in no uncertain terms that I wasn't DMing properly, and that they weren't going to play in my campaign any more.
That was 1981. I was sixteen.
A bit later they lit