You may consider this to be one of the most common sewing tools, but it is also the most indispensable, at least for myself.
This especially true if you do a lot of hand sewing and basting. I do my hand sewing using finest Japanese hand sewing needles; and if you have worked with those you know that they have the tiniest needle eye possible. Even with perfect vision and finest motor skills, threading these needles may prove a challenge.
However, the needle threader is also useful for pulling loose threads to the wrong side of the garment, as well as repairing fabric snags.
It's always useful to have several needle threaders at home as they tend to disappear. Yoiu can buy needle threaders on Amazon, eBay, as well as any sewing notion store.
They can be made of plastic, metal, silver and wood. They may be basic or more elaborate. Below are some examples of threaders I found on eBay.