OK, I guess I'll start by addressing the topic. I think you really did nail the question, but I also believe one point needs to be reiterated; any knife you carry should be readily usable as a utility knife.
Someone started a statement with, "In an ideal world..." Well, in an ideal world, we would have no need for defensive weapons. In a slightly more realistic, and more desirable than real world, knives would be a lot cheaper, come in pairs, and NOT be comfy for multiple grips, but in the one each individual prefers. In the meantime, there are 4 folding knives (since most of us can't carry fixed blades on a regular basis) which are clear "bests" in this category. They are the REKAT Sifu and Poket Hobbit (That knife looks EVIL! Ya gotta love it!), and the Cold Steel XL Voyager/Gunsite and Vaquero Grander/ El Hombre. This breaks up into 2 price levels and sizess.
To address preparation... a cell phone might come in handy, and is VER RARELY considered a weapon. If you REALLY want to be EXTRA prepared, you could always hire SWAT team to act as your own personal protection unit, and carry a big tent in case you ever get lost in the woods. In the meantime, try a good all-around folder and a cell hpone (for non-students, which exludes me from either one, but I carry a knife when not in school, and OCCASIONALLY) at school. Sorry about the ranting, but I don't think any of it was off topic.
Howie