In a medium saucepan, bring the water, butter, and salt to a boil over medium-high heat. Add the flour all at once and stir quickly with a wooden spoon until the mixture forms a ball; remove pan from the heat.
Add 1 egg and beat with the wooden spoon to blend. Add the remaining eggs one at a time, beating after each addition. When the dough is smooth, spoon 1/4-cup mounds of dough onto a cookie sheet, leaving 2 inches between each dough mound.
Bake for 40 to 45 minutes, or until golden and puffy. Transfer the puffs to a wire rack and let cool completely. With a sharp knife, cut puffs in half horizontally before filling.
For Lunch or Dinner: Fill puffs with tuna, chicken, egg, or seafood salad.