Something important disguised as something unpleasant, or explicitly labeled as uninteresting.
Do We Have This One?? Seems odd that we don't. If not, Needs More Examples. I think I've seen this lots of times, but I can't think of any other examples off the top of my head. If a character has something they don't want anyone else messing with, there's many different ways they might hide it. They could explicitly claim it's not what it is, but any decently smart person will see through that. They could put it somewhere no one is likely to look, but someone could stumble upon it anyway. Or, they might use this trope: leave it in plain sight, but dress it up as something repugnant. Chocolate hidden in a box labeled "Dried Broccoli," for example; or a button that produces free money marked "Begin Math Test," or a questionable DVD in the box for Ishtar. If you're feeling particularly unsubtle, put a sign on it telling people to pay no attention to it. Similar to Hidden in Plain Sight, but with something added to convince people to stay away (which often backfires).
- The gigantic robot complex in Gunnerkrigg Court, the entrance to which is labeled "Boring Door." This isn't much of a deterrent, of course.
- Pokemon lampshades this in one game, where a Team Rocket hideout is disguised as a gift shop, with a sign that says something about "just an ordinary gift shop, nothing to see here..."
- Mystery Science Theater 3000: In Joel's last episode, the escape pod was finally found only after many years, because it was hidden in a box labeled "Hamdingers" - which was explained by the characters to be an awful snack food no one would really want to eat.
Hello, Unknown Troper. You'll need to get known to lend a hand here.