I recently ran a heavily adapted version of the first adventure in The Gem & The Staff, a 1983 module by John and Laurie Van der Graaf of TSR UK. Meant to be played at conventions with one DM and one player, the module includes a pair of linked adventures in which an 8th level Thief (Eric the Bold) must rob a pair of powerful wizards.
The adventure has a lot to recommend it. With a real-world time limit of 30 minutes per adventure, both adventures combined only take up 14 pages but manage to fit in a variety of tricks, traps, and opportunities for clever solutions into that space. Apart from his high-level Thief abilities, Eric’s player has an interesting toolbox: a magical sword and dagger, a powerful sleeping potion, a shrinking potion, and a Ring of Spell Storing loaded up with a variety of utility spells. The ring and the two potions give the adventures a bit of a point-and-click adventure game feeling, but to the writers’ credit most of the encounters can be solved in multiple ways. For example, several monster entries note how they could be tricked into drinking the sleeping potion. Most of the combat encounters are far too dangerous for a single PC (a hydra guarding the castle drawbridge can easily kill Eric in a single combat round), but they’re telegraphed and clearly designed to be tricked, snuck past, or avoided rather than fought.