I'm thinking a drinking horn. They're generally made of pretty low density materials, are hollow for obvious reasons, and can easily come with something to hang them on which doubles as a carrying strap while getting it to the giants. You can decorate it pretty dramatically, and just having a sufficiently massive horn sends some nice messages about the value of not messing with you.

Plus, if that magical apple tree isn't being used by a giant living alone to make booze I'd be surprised.