Cut the celery and any other vegetables you’d like to add into a small dice so it’s still easy to make a sandwich. 1 to 2 tablespoons of chopped sweet red bell pepper, dill pickle, pitted olives, or water chestnuts are all good stir-ins for the tuna salad. Mayonnaise, lemon juice or vinegar and seasonings. Stuff tuna salad in hollowed out tomatoes or avocado halves for a fresh take on lunch. Swap out the tuna for chicken or ham, adding some Dijon mustard with the mayonnaise in the dressing.