That is so strange about the BK7. It was my first Becker, and on the surface I was most excited about getting one...and I figured it would be my most used blade in the outdoors, but quickly found a BK9 in my possession. Several times I have strapped the 7 on my side, but end up quickly digging out my 9 or 16 (now my BK15) and putting the BK7 away again. Never would have thought...
Back on track...
My least used Becker - my BK11.
Most unused knife overall? I have boxes full of them...thus is the journey of many a knife nut. We keep buying knives we think will meet the exact need we have...until the next "better" knife comes along.