This really has nothing to do with programming. But for a while, I had a kind of hobby (/obsession) with collecting as many potentially useful things as possible in my bag (useful for me or others). It had to be comfortable to carry though, so I had to take size and weight into account.
Things like a presentation pointer/remote, waterless stain remover, all kinds of chargers, earbuds, plastic bags, painkillers, bicycle lights, hairgel, compact snacks and lots more...