Brightly colored plastic mini accessory carabiners strong enough for keys or coffee mugs.
A regular plastic accessory clip, these can be used to fasten, e.g., light items to the chest. Cheap and does its job. I can't say about durability yet, as I've only been using it for a short time. It's unlikely that it will break right away, since there is so much thick plastic and it's mainly used for hanging shoes.