D&D One Shot

The PCs are chaotic criminals who must discover the plans of a venerable hag. The mood might be... tense
There is a repulsive noble who betrays them partway through.
The characters start at a burning tavern. Partway through they encounter an invisible wall. If things slow down something goes missing.
Afterwards there is a tavern burning down. Possible sequel... a clue from a reward or treasure points to an infamous dungeon...

The PCs are lawful hermits who must befriend/tame a repulsive yuan-ti. It might involve criminal organization.
There is an intimidating assassin who comes with them.
The characters start in a fight. At some point there is a local festival. If things slow down they discover an unexpected place to rest.
It finishes with a reward of membership of an elite group.

The PCs are brave halflings who must subdue a vain devil. The mood might be... action
There is a talkative dragon turtle who tries to help them. they are the drinking companion of a character.
The characters start at a disrupted wedding. Early on they encounter a puzzle trap. If things get stuck something starts following the group.
It finishes with feasting in an inn.

The PCs are imprisoned warlocks who must slay a venerable yugoloth. It might involve winter.
There is a drunk mercenary who offers them aid.
The characters start during a heist. Early on they encounter a guardian monster that hinders their progress. If things slow down a prisoner escapes.
It finishes with a reward of a grand feast.

The PCs are outcast folk heroes who must deliver a golden chest. The mood might be... whimsical
There is a popular thief who betrays them partway through. they are the aunt of a character.
The characters start in a tavern brawl. At some point they meet a lover of a character. If things are going nowhere a magic item develops new powers.
Afterwards there is one character narrating about all of the others. Possible sequel... a foe returns more dangerous than before