Really? A good knife is what you want.
Absolutely terrifying in a grapple as they're wickedly fast in the hands of a competent knife-fighter and come in from all directions. However the problem with them is that the same goes for the other guy. This is an ancient sword fighting doctrine known as The Paradox of Defence and it still holds true. The concept is that it's absurdly easy to kill a person with a weapon, morons do it all the time. So that means it's easy to kill a person but conversely hard to stay alive, and from experience I can tell you the closer you get then the harder it is to achieve. In the 1300s the famous sword fighting teacher Johannes Leichtenaur stated "God have mercy on those who take daggers into their hands".
So, in that case you might start thinking "why not a short fighting axe?" After all they have a bit of reach and they're not a grappling weapon like a short blade. Easy to carry, they pack a powerful punch and a back-spike can go through armour. If you have decent, unbroken ground under you and you have a passing knowledge of footwork you can sit back and kill anyone. After all, you can still carry a utility knife if things go south and you have to grapple.
However if you have both hands free then you can carry something truly frightening. The most terrifying thing I can think of to face is a hedging hook. It has the mass so you can't deflect it easily and the reach to sit back and butcher an opponent. it can shear limbs off with a single swipe and it's a superior machete. So yeah, if I can carry a short blade as well I'm going with this bad boy.
