Any item can be turned into a magic one by assigning it supernatural properties. We have some standards to choose from, such as rings, bracelets, and other jewelry, and the stereotypical wizard’s staff. By contrast, a wand is something no one has unless they’re a wizard (or a classical music conductor). Every item we see around us can be given magical properties, but we shouldn’t make everything magical unless it dominates our setting (even then, moderation is best). How do we decide on a limit?
One way to create limits is to invent problematic items. For example, a cloak that always makes us invisible is an issue because we must securely store it somewhere when not in use. Make an item difficult to control and people will avoid using it. Study how real-world tools you use malfunction, then imagine how the invented item does this. Is the item defective? We can have fun with this, such as that cloak making our body disappear but not our shadow and the character not realizing the cloak doesn’t take care of both. Does it sometimes go on by itself? Is it expected to deteriorate in time? Does it have the coveted “on/off” property?
Not all items are created equal and we can have different versions of anything. Poorer characters might get by without features while wealthier ones expect them. The existence of some features might not be apparent to some users, or they could assume one exists and be disappointed that it doesn’t. Maybe they even counted on it and found out at the worst time that their assumption was wrong. We can use such things to aid story, as tales where everything goes as planned offer less tension.
Limit an item’s unique powers through quantity and quality or our characters have too much power. Most magic items have one or two related uses, which is sensible, but a wand or wizard’s staff are exceptions because it’s seemingly their nature to provide assistance on a wide array of matters; they’re also controlled by those with talent, skill, training and more, which may be untrue with other items. For everyone else, dividing up abilities helps us focus and not create the equivalent of a Swiss army knife.
Some items are sentient, but the infamous talking sword has become a symbol of unimaginative writing; some magazines immediately reject a story with one. Getting away with such things has much to do with originality and whether it’s downplayed or in the audience’s face. We may have better luck with SF where an AI can be the source of that speech.