This is adapted from the tuna salad at Noah's Bagels. The dill and green onion add a fresh herby flavor, the celery adds a satisfying crunch and the minimal amount of mayo makes this much more like a salad than the tuna goo normally presented as tuna salad. It's quite good in a sandwich (or bagel!) as well - it helps to use your hand or an ice cream scoop to compress the salad onto the bread.