The stereotype of a "knife fanatic" as a usually young, dumb male who harbors latent insecurities is not always the truth. I haven't seen many but two always come to mind. One's actions (back in the mid 1970s) resulted in the carrying of all non-issued sheath knives being banned in 1 CBG. During a BAA ex in the Sarcee trg area, he became a little exhuberent while playing enemy force (even though he wasn't supposed to be with them) and nearly severed the thumb of a 1 Fd Amb MCpl MSE Op. What made it more strange was that he was a doctor and the CO (. . . Rene in the bush).
It's odd that the other knife nut I ran across was also a doctor, but in the USAF. I met him on a cold dark night on the ramp at Ramstein Air Base. An evac flight from downrange (it was during Desert Storm) had recently arrived and we were unloading the patients and moving them into the ASF. As I was surveying the activities, an individual left the plane and came over to me with a couple of questions about onward evac to hospital. Though he was dressed in typical flying clothing (flight suit and jacket), he was also wearing webbing and a helmet. There were knives attached (hilt down) to each of the shoulder straps, a knife was on each hip and smaller knives strapped to each of his boots (his flight suit was bloused over his boots). It took some control not to laugh in this senior officer's face.
Is having a non-issued knife useful; I would have to stongly agree. I've had one and have been carrying the same item since the late 1970s (both in uniform and out). I've used it frequently on course, on exercise and on operations. I bought it at the Sally Ann in Lahr (actually I bought a couple - they were only a few marks each). It's a Swiss Army penknife (a very small blade, a file/screwdriver, a scissors, a toothpick and a tweezer). Most often it's on my keychain, though I have also clipped one to my dogtag chain on occasion. I've occasionly carried a belt knife in the field and when we were issued multi-tools that also became an item to consider, but no other edged implement has been as useful as that tiny little red knife.
