One of the most overlooked pieces of fishing equipment are sunglasses, yet they are, in my opinion, one of the most essential. Polarized sunglasses will help anglers, whether it be wading or in a boat, see beneath the surface of the water. This helps with spotting structure such as drop offs, sunken debris, weed beds and occasionally even fish. To a wading angler they also help you to wade safely aided in spotting deep holes, sunken logs etc. all of which can cause spills resulting in wet waders or worse.
Sunglasses can help in many ways and should always be used
Sunglasses also can help save your eyes from errant hooks or flies which can cause irreversible damage. If you have ever witnesses someone get a hook in the eye it is something you wish for no one, especially yourself. Wrap around style of glasses can also help block the wing from the front and sides, preventing the irritation that wind can cause. For anglers that wear prescription glasses that don't want to invest in a pair for fishing, clip on lens are available for most glasses shapes as are "Fit Over's"
These are basically a second set of sunglasses that go over top of your prescription glasses. They also have the benefit of wind blocking side shields, they aren't very stylish but they work. The color of lens you chose is based on where and when you are fishing, Brown is recommended for most freshwater situations, Gray for saltwater and Amber for low light. As long as they are polarized, to cut the surface glare and help you see into the water.