Thoroughly drain the tuna and place in a large bowl.

Slice avocado in half, removing the peel and pit. Mash one half in a small bowl, and dice the other half. Set diced avocado aside.

Add lime juice, mayo, and salt & pepper to the bowl with the mashed avocado. Mix well, then stir into the tuna until well incorporated.

Fold diced pickle, red onion, celery, and cilantro into the salad along with the diced avocado. Season to taste with salt and pepper if desired.

Serve inside pieces of lettuce, stuffed into a tomato, on crackers, or in a sandwich. Cover and refrigerate leftovers if necessary.