Boker Plus Cutweazle Folding Knife
I have a collection of utility blade knives and this is one of my favourites. The button for adjusting the blade is sprung so the blade is quickly deployed into one of three different positions. The blade is easily changed and it fits many easily available utility blades, I use Hultafors which are available on HH. It is very light weight and quite small. Overall a well designed and robust knife.