There/Not There was my first thought, too. You cast it on an object; each time a viewing creature stops looking at it and then looks again, the object has a 50% chance of not existing for that creature. Items can exist for some creatures and not others simultaneously. HILARITY ENSUES.
The other that pops to mind is Frisky Chest. Third-level, I believe, probably wizard. Whenever someone disallowed comes within a certain radius, the target object grows feet/wings/fins, immediately running/flying/swimming away at a very high rate of speed. There are detailed rules in the spell description for how it could and could not be caught. It would run away to a safe distance, lose its appendages, and wait, ready to run away again. Hilarity once more ensues if your players are at all in the mood for the game.