The title says all. You know, those small adventures that you can place into any campaign, or for the larger ones, turn into one- or two-shots. What's your best one? Here are some of mine, most of them are quite ridiculous because who doesn't love a fun and silly one-shot (also feel free to use them if you want):

• A band of musicians who are actually warlock cultists, corrupting and stealing all valuables from their patrons with their beguiling music, then offering the stolen goods to the god they worship. The players must terminate the band members before they cause any more havoc.
• A tiny village called Mandrake Hill is suddenly missing its town sorcerer who protects the village. It's a very elaborate mystery (which they did in fact solve) and involves the sorcerer having received a pay raise (it's very complicated). Basically he was eaten by an [Tooltip Not Found].
• The players decide to go on a vacation! A travel agency helps arrange a relaxing holiday to the Astral Plane, but their portal to get there malfunctions and sends them to an Astral sub-Plane ruled by a tyrannical Giff warlord. The players must either escape or deal with the warlord by infiltrating his cosmic fortress.
• This is more of a level-20-style "Everybody can DM" one-shot. The players are so well-liked and so powerful that even the Gods adore them, and so the gods have made a special demi-plane for them called The Godhall. The Godhall is basically a series of challenges and games, each run by a different god, and makes the players think in every aspect and fight unimaginable foes.

What are your best one-shots (and mini side-quests)?