These higonokamis are universally popular as a do-everything penknife. The Japanese-equivalent to the Swiss Army Knife in terms of popularity, they were originally used to sharpen pencils but can be used in almost any crafting task and for household jobs, particularly box opening. 

Mini brass: 3.5cm blade; 9cm unfolded length

This tiny version is perfect for your key ring and still suitably ferocious for box opening and string cutting. 

Group picture, top left to bottom right: Handmade brass, regular brass, black mono and mini brass.