There are many travel adapters on the market. Here are a few that we have tested and liked, but didn't make it above for one reason or another.
Ceptics 65W World Travel Adapter for $55:This versatile adapter comes with slide-out plugs in types A, B, C, E/F, G, and I. They fit into the rectangular brick and plug directly into the outlet, or you can attach them to the optional 5-foot cable. The brick features a grounded U.S. plug and a second ungrounded plug, with one USB-A port (30 watts) and two USB-C ports (65 and 33 watts) on the other end.
Masterplug Visitor to UK Travel Adapter (3 Pack) for £12:For visitors to the UK, this simple trio of adapters accepts European, American, Australian and Asian plugs. They are single-socket adapters with 13-amp fuses inside, and they work perfectly. These are the adapters I use for long-term testing of appliances from the US and elsewhere that don't have UK plugs. If you forgot to buy an adapter before you arrived in the UK, you can find this three-pack for a great price in any Argos store.
Anker European Travel Adapter for $16: One of our favorite portable charger brands, Anker also makes travel adapters. This one plugs into most European outlets to give you a single grounded US plug, a USB-A port, and two USB-C ports. Unfortunately, the three USB ports max out at 15 watts total, so it's best to charge overnight, but I appreciate the temperature and overcharge protection. There's also a UK version ($16).
Ceptics Travel Power Strip for $35:Much like the World Travel Adapter Kit 2 above, this small power strip offers two grounded US outlets, but it only has one USB-A port and one USB-C port, and instead of plugging directly into the wall, a cable connects to an interchangeable plug head with Type A, B, C, E/F, G, and I adapters. The adapters can be tricky to change, but otherwise it works well.