I've always wanted a hip flask. I didn't actually get one until I was bought one as a present recently. It now sits proudly on my shelf, full of rum! There's something old worldy about them that I love. In a world of plastic and disposable bottles they represent the old way, the spend-on-quality-and-it'll-last way.
The modern shape of hip flask is curved to allow it to match the contour of the wearer's hip for discrete transport. They've been used to hide a cheeky drink on pilgrimages, keep illegal alcohol hidden from Prohibition police and spice up many a dull party since the 18th Century.
They also just look great.
…but I digress.