Aside from small opening night gifts that never seem to get unpacked from my kit (like a cigar cutter and glow-in-the-dark, ahem, massage oil), I do have an 'egg' filled with Silly Putty. This too glows in the dark and I have slapped it on the occasional 'whackable' corner of a set backstage. Also useful as a 'fidget stone' for those who need it....