I lean toward the philosophy of having a knife (knives) that increase the odds of having a knife with you when the need arrises. Said another way "The best knife is the one you have with you."

For me, I can't carry a fixed blade to work, so I carry a mini-Rittergrip. It works for me.

I recently had a scare where I thought I'd lost the mini-Rittergrip (I hadn't), so that prompted me to buy a Kabar Dozier Spearpoint ($20) that I carry when going somewhere where I think there is a higher chance of the knife coming off my pocket. I still wear the mini-Rittergrip to work though.

When out camping with the Scouts they don't allow fixed blade knives, so I carry a fullsize Rittergrip and a SAK.

When camping with my family I sometimes carry a fixed blade knife in addition to the fullsize Rittergrip and the SAK. I have a BK10 Crewman and a few Moras. In general the Moras get more use. Each has advantages. I am anxious to see Doug's upcoming Benchmade fixed blade knife.