I think that it would be extremely difficult to find a fixed blade that would excel at being both a utility tool and weapon. I don't know jack about using knives in a weaponized role, so take my opinion for what it's worth...
I'd check out a Benchmade 176 SOCP as a weapon retention and defensive tool, or maybe the 178 (partial serration) for a little more utility factor. The SOCP is a slim, light package (under 3.5oz with sheath) with versatile/discreet carry options. Benchmade released some YouTube vids with the designer Greg Thompson demonstrating the knife and its benefits.
[video=youtube;jctUT_IJ0lQ]https://www.youtube.com/watch?v=jctUT_IJ0lQ[/video]
Maybe the SOCP would make a good weapon but it's a pretty lousy design for an actual cutting tool, imo. If you want a blade for utility use, I'd add a waved Spyderco Endura folder.
But if you have your heart set on a compromise between utility and self-defense in a fixed blade, maybe check out TOPS Knives. If you can get past the ridiculous mall-ninja names they give their knives, you may find TOPS can make a decent quality product and offer several different models/shapes/sizes.
Anyway, good luck in your search and stay safe out there!
-Brett