Prepare grill. Toss shrimp with 1 Tbsp. oil. Transfer to grill and cook, turning, until charred and firm, about 5 minutes. Transfer cooked shrimp to a large salad bowl.
Brush bread with remaining oil and then grill, turning it occasionally, until toasted on both sides, about 5 minutes. Rub toast slices with garlic clove. Transfer toast to a board and cut into cubes; add cubes to bowl with shrimp, followed by vinegar, lemon peel and salt. Toss mixture well. Add arugula and tomato, season with pepper, and toss again.