I myself can now hang a beer bottle neck through and it just hangs there - fark knows why i tried - yes i can fit my headphones through and hang when not using, i used a coke bottle lid for a while, when i couldnt be bothered buying any plugs between sizes.
ALSO great for popcorn storage LOLS
hmm mates have had usual cigarettes, $100 notes rolled up, joints etc... umm another mate in highschool lost his plug at the show and put a stick through it that he found... oh and ive seen dudes with coke cans in at a show, that was epic rad!