Hands down, it's storms. She's an outside mostly cat and very adventurous so not much shakes her up, but a big storm with lots of lightening and thunder will have her leaping into my arms! Last night we had a big one roll through here and it was about time for me to bring her in to be with her kittens anyways, so I decided to go ahead and grab her up. As I opened the back door to call for her a bright flash happened and a very loud roll of thunder. She bolted across the yard and actually leaped up onto my chest, into my arm. Her heart was just racing, bless her heart! She nuzzled into me and seemed very happy to nestle up with her babies after that!