Addressing targets- Martial arts generally teaches one to disable an opponent, by and large, and not kill them outright (not including the Sambo/Krav Maga crowd here, who are very happy to inflict lethal damage) as it is often taught from a defensive point of view. There's absolutely nothing wrong with this, and I am a happy student of Aikido because it gives me the less-lethal options for taking down an opponent. However, I work overseas a lot where kind-and-fluffy gets you killed, thus I also study Krav for the opposite reason, and you pick up some VERY nasty, brutal and incapacitating/lethal techniques. Here's some key pointers born of that when it comes to targets-
1) Neck: While it might seem to be a choice target, the neck is surprisingly resilient and hard to find a vital spot with a small puncture-based weapon. I've seen an operator shot through-and-through in the neck by a 7.62x39 round, and the SOB was still up and kicking, trying to return fire. Keys are much more blunt than knives and such, and might not even get through the skin. There are many layers to the skin and sub-skin structures- dermis, sub-dermis, cutaneous (fat-tissue) and subcutaneous membranes- before you even get to the muscle and primary blood vessels. The chances of getting through all of that and hitting something vital- carotid, jugular, trachea, etc.- make it a difficult target to ensure lethality or incapacitation on, and that's not even taking into account reflexive defensive tucking and blocking.
2) Eyes: Excellent target, if a bit hard to hit. Gripping the keys in the fist where they stick out like punch-daggers, you can strike the eyes with moderate success. Despite being hard to hit due to size and reflexive defenses on the part of the opponent, it is a priority target due to being a fight-ender. Most people will desperately want to be somewhere else when their eye is put out. It's a psychological blow as much- if not more than- a physical one, as the eye does not repair itself to usefulness again and humans reflexively freak the hell out when they lose one.
3) Groin: Due to jeans and other clothing, the groin is a bad target for something as blunt as keys. Knives, spikes, 16 penny nails, etc. are all viable since they can punch through the clothing, but keys are generally too blunt. However, if clothing is not an issue for whatever reason, the groin on a male is a prime target. Behind the... danglies, shall we say, is a knot of blood vessels, including high-volume arteries that feed into the femoral. Puncture these, and your target is toast. There are no pressure points or tourniquet application points to stem the arterial bloodflow in that area, and your target will bleed out into unconsciousness in under a minute.
4) Hands: Something people really don't think about with key-fighting is the hands. Rap a ring of keys across the knuckles, and it stings. Stab keys into the hand from the top, and you could incapacitate them.
just a few items for thought