Fell Hack – Go Whistle
A literal hack this. Modern plastic whistles are great; light, loud and kind to your lips in cold weather. They are however, difficult to keep hold of, and have a bizarrely useless clip on the back.
Solution? Chop the clip off, smooth the burr (a flame helps, plastic is difficult to file neatly). Scratch some light cross-hatching into the slippy plastic with a knife tip too. You now have a neater whistle, with a thumbstop and roughened surface that makes holding it easier; and to top it off, saved about 1g of weight*.
*no, I’m not actually claiming this as a serious point; though it would mean room for an extra peanut M&M or two …