In a game module in the Star Wars RPG, a couple of Squib merchants arguing with another group of merchants near the entrance to a ruined Jedi Academy have a burned out lightsaber for sale. This lightsaber allows you to interact with an important NPC later on, finding out some key info.
Many of the Fighting Fantasy gamebooks published in the United Kingdom have the reader collect all sorts of strange odds and ends, most of which seem to have no possible justification for the adventurer taking them along. Naturally, those seemingly useless items end up being just what the reader needs to get him- or herself out of trouble, or otherwise make an enemy easier to defeat.
Exalted mentioned in the first edition that one of the daughters of the Scarlet Empress had followed her into the Imperial Manse one night and simply disappeared. It would only be deep into Second Edition when Lillun returned. Unfortunately.
Also worth mentioning was the AI "Eyem," named for the first thing it said to those who discovered it, a throwaway mention of a wonder of the First Age, or at least the Shogunate. Again, fast forward to the second edition, where the First Age version of the internet is a sentient network known as I AM.