You don’t need a fancy tool or a chef’s diploma. Just grab a small knife, make a shallow slit along the shrimp’s curved back, and pull the dark thread out with your fingers or the knife tip. Rinse it under cold water, and done. It takes about 15 seconds per shrimp once you get the rhythm.
Another trick: buy “easy-peel” or “deveined” shrimp from the store. They’re often already split and cleaned, saving you the dirty work. It costs a little more, but if you value your Saturday afternoon, it’s worth every penny.