Popeye had it right years ago when he said "I'm strong to the finish cause I eats me spinach..." Spinach is just awesome, packed with protein, vitamin A, vitamin K, magnesium, folate, manganese, iron, calcium, vitamin C, vitamin B2, potassium, and vitamin B6. Plus, it also has selenium, an important nutrient that many people lack in their diets.
I need a lot of protein in my diet and this is one of the many foods that I try to have every day. I usually cook it, but it's great raw too. Just make sure you wash it well or buy organic. Spinach can have a lot of pesticides.