The 5/8 in. Spark Plug Socket, 6 pt. Flex by Craftsman is the best spark plug socket available because of its nickel chrome plated design. This plating makes the socket resistant to rust and corrosion. This is great if you don't plan on using it very often and it will be stored in your garage, where weather exposure is more common. I also love the flexing feature of this socket. It makes the tool more valuable because it increases the easiness with which you will be able to reach the sockets in your vehicle. That's a good feature to have if your car has spark plugs in a hard to reach or tight place.
Tekton 3/8 in. Drive x 5/8 in. Extra Long Spark Plug Socket
The 3/8 in. Drive x 5/8 in. Extra Long Spark Plug Socket by Tekton is great because of its black oxide finish. Black oxide finish is great to have in a tool because it not only reduces corrosion greatly, it also cuts back on the amount of light that the tool reflects. If you have ever worked with a chrome plated tool in the hot sun for hours, you know how hot they can get. If you live in a place that sees lots of sun, then this is a great tool to consider. This socket also has a notched drive end. This will lock the socket onto whatever ratchet or extension bar you use it with, which is a great thing to have if you're at all worried about dropping your socket.
I have included the 80546 5/8-Inch x 6-Inch Swivel Spark Plug Socket by GearWrench on this list because the entry point of the socket (where you place the socket onto your spark plug) is angled down. This helps make changing your spark plugs easier by guiding entry. An angled entry point is good to have if your spark plugs are in a tight place that doesn't offer a whole lot of visibility. This tool is also a swivel spark plug socket. What that means is that the socket swivels in different directions to allow the socket to reach strangely angled or hard to reach spark plugs. When you combine these two features, you get a socket that is great to have because it makes even the remotest spark plugs simple to take out.
Duralast/3/8 in. Drive 5/8 in. Spark Plug Socket
The Duralast /3/8 in. drive 5/8 in. spark plug socket is a solid choice because the plug retainer relies on a magnet. This allows it to grip the plug you take out a lot better. Most spark plug sockets that have a retainer use rubber, so the magnet makes this socket a lot better in terms of grip. This is also great if you ever end up having to use your socket in the rain, where the water might affect rubber's gripping capabilities. That won't happen with the magnet. This socket also comes with an elongated extension bar, giving the socket an overall length of around 15 inches. If you have spark plugs in awkward places, then this socket is perfect for you because the extension bar eliminates the need to stick your hands down into the engine.
Performance Tool 3/8in. Drive, 5/8in. W80533 Extended Spark Plug Socket
The Extended Spark Plug Socket 3/8in. Drive, 5/8in., Model# W80533 by Performance Tool (Wilmar Corp) is great because of the quality you get for the price. At around $5, this socket is incredibly easy on the wallet. Plus this socket is also deeper than other comparable tools at 5 inches long. This extra length is good if your spark plugs are in a hard to reach place and you don't have an extension bar to use. The final reason I have decided to include this tool on the list is because it has a knurled design. This increases the grip of the socket, which is good to have if you ever get sweaty palms while working.