I really like Oliclips. The magnets are pretty strong and so you can use them as bookmarks, money clips, paperclips, fridge magnets, pen loops or to close food packets. I have even used them as hairbands in an emergency.
I have had the ones above for about three years now but have recently bought some more, in various metallics from Etsy. They often have discount codes so keep an eye out.
They come in two sizes
and many different limited edition designs
Or just plain ones