It'll be the one I have at hand, won't matter if the truly greatest one is sitting at home in it's queen chambers, when you have something that needs cutting right now, so what ever you carry, keep it clean, sharp and near at hand, as you never know when you'll really need to call on it's edge to be pressed into work. I have traveled to a lot of places around the world, in glass container manufacturing plants, in Mexico the mechanics at one plant had old hacksaw blades with electrical tape for a handle, this is the regular hacksaw not a power saw, in Bulgaria the workers there, when they had to cut some rope or plastic would take a piece of broken bottle, glass is sharp remember

and they would use that to make the cut they needed at that time.
Carry the best, most functional knife you can, but for the sake of this thread, right now, it's the Spyderco Resilience for powerful cutting performance, a large enough blade for any task and a very very quick opening method via the thumb hole, I use the right index finger flick and wow, it's very fast deployment !!!
But, it all counts for nothing if it isn't with you!

G2