DnD: Roll for Initiative!

I’m outfitting a “magic” shop with items that have magical sounding descriptions but aren’t actually anything special. For example:

Rock of gravity - hold the rock out at arms length and drop it. This not only tells you whether or not you are within a gravitational field, but also which way the gravitational field is oriented!

Ring of Cat Speech - put it on to be able to speak to cats! It is not proven whether the ring actually works or that cats can understand you but choose to ignore you.

Looking for more ideas! Thanks!