One of our scuba diving newbies, didn't know you could rent lead diving weights > he brought 20 lbs of lead in his suitcase.
We brought an electric ice-cream maker one time (more than once) with a few interesting stories there.
My high-school daughter and her high-school girlfriends brought a four-person, nylon tubing, water-balloon, sling shot > everyone in the mooring field was "fair game"