Breathing is definitely a good one if you can do the proper techniques and keep yourself from getting distracted.
I also like to think positive thoughts, remind myself that I am causing my panic attack and I have the power to stop it. I imagine myself calm, relaxed and breathe deep...
Another good one for me is coloring, but not possible on full panic cuz of the shakes. Lol
And family/happy movies will usually calm my panic enough to allow me to sleep when I'm awake from panic at night.