Pour the Tajin seasoning onto a small shallow plate, spreading it evenly across the surface. Run a lime wedge around the rim of each shot glass, making sure to coat the entire edge with juice so the seasoning will stick properly. Dip each moistened rim into the Tajin at a slight angle, rotating gently to create an even coating. For extra flair and flavor, brush a thin layer of chamoy sauce on the inside rim before adding the Tajin.

Roll the limes firmly on your counter with your palm to break down the internal membranes and release more juice. Cut them in half and squeeze until you have 2 full ounces of fresh lime juice, straining out any seeds.

Add the watermelon vodka, fresh lime juice, simple syrup, and hot sauce to your cocktail shaker. Give it a quick stir with a bar spoon to ensure the hot sauce doesn't settle at the bottom.

Fill the shaker about two-thirds full with ice cubes, then seal it tightly. Shake hard for 15 to 20 seconds until the outside of the shaker becomes frosty and cold to the touch.

Position the strainer over your shaker spout and pour the mixture evenly into the four prepared shot glasses, being careful not to disturb the Tajin rims. Fill each glass to just below the rim so there's no spillage.

Add a small lime wheel to the rim of each glass or a tiny watermelon wedge if you want extra visual impact. You can also drizzle a few drops of chamoy inside each glass for added tanginess and presentation.

Serve the shots right away while they're still cold. Instruct guests to lick the Tajin rim first, then shoot the liquid in one smooth gulp, finishing with another lick of the rim for the full sweet-spicy-tangy-salty experience.