USB to 5.5 x 2.1mm adapter.

This is handy if you need to power a device with a 5.5 x 2.1mm "barrel jack" and have a spare USB cell phone charger, or a port on a power bank handy. These accept a USB-C cable and either pass 5V through or boost to 12V (note at 12V you'll get about half the rated current out, so a 2A charger will yield about 1A of 12V). This may save having to get another 12V wall wart for example.