Place the shrimp on a small plate and season with salt and pepper. Cut the avocados lengthwise around the pits and remove the pits. Cut the avocado flesh in a crosshatch pattern and use a spoon to scoop the avocado flesh into a medium bowl. Combine the avocado with 1½ tablespoons of the lime juice and the cilantro and jalapeño.
Use a knife to remove the skin and any pith from the grapefruit flesh and slice along the membranes to remove the segments. Set aside.
Brush the baguette slices with olive oil and season with salt and pepper. Place the baguette slices in the toaster and toast until golden brown.
In a medium skillet set over medium heat, heat 1½ tablespoons of olive oil and add the shrimp. Cook for one minute on one side, then flip and cook an additional 30 seconds on the other side. Transfer the shrimp to a bowl and toss with the remaining ½ tablespoon of lime juice.
To assemble: Spread 2 tablespoons of avocado mixture on each baguette slice. Top with one or two pieces of shrimp and a segment of grapefruit. Sprinkle pistachios over the top and serve immediately.