I'll chime in with another vote for the Kershaw/Ken Onion rainbow Leek.
Very pretty knife. (Almost girlishly pretty.) Large enough to be useful in a fairly wide range of situations, including self-defense. (The rainbow Chive is equally pretty, but too small for many purposes. But ultra-compact knives have their place, too.)
Reasonably priced. Nifty "Speed-Safe" assisted-opening system, which manages to stay on the safe side of the law in the vast majority of places. Decent, if unremarkable, materials and craftsmanship, from an okay company.
I admit, I may be slightly biased. My rainbow Chive (the Leek's smaller brother) arrived in yesterday's mail, and I expect to pick up a rainbow Leek pretty soon.
Really, though, a "knife that could be used for self-defense" is almost as broad a category as "paper that could be used for writing." I mean, some knives are more suitable than others, but nearly any knife would do fairly well in a pinch. (Well, maybe not the steak knife I was given at a local restaurant, the other night. But I tend to categorize that more as a butter spreader, than as an actual cutting instrument.)