Hi Squid,
Well, I don't know of anything that matches your original request, as your original request conflicts with itself a bit... To illustrate:
(Your original post, with my comments)
I'd like for it to give me some degree of self defense.
Okay, cool. First we need to establish what you mean/understand about realistic self defence training, and what you mean by "some degree". We'll cover this as we go...
I'd like for it to include real sparring and maybe even a competitive fight occasionally.
Right. Competitive aspects are very different from self defence training, to the point that competitive training can actually be a detriment to your abilities to defend yourself. This is due to a number of factors, including but not limited to the constraints of rules, a focus on non-effective techniques and other training methods specifically designed to aid your competitive success, the development within yourself of a false sense of the realities of violence and how it occurs, and many other aspects.
To note, though, I am not saying that competitive arts and training is not effective, and will offer no benefits, just that you should be aware that it is not geared up for self defence, because that is not it's purpose.
I'd prefer it were a hard martial art.
"Hard" can again be a very subjective term. I can, for instance, take students through very hard (physically) training, including a lot of very intense physical work, a lot of impact, and constantly pushing them. I can also take them through very hard (psychologically) training by pushing boundaries and their ability to handle very high stress situations. I can also take them through very hard (physiologically) training, by taking them through adrenalised training, giving them a small or large adrenaline dump followed by the endorphin rush, then repeat. I can also take them through very hard (emotionally) training, pushing them to go beyond what the know as real, challenging beliefs and values in order to go further in their journey to reach their potential.
Oh, and we do cover all of this, by the way, and I would consider any part of it "hard training", but certain aspects are harder than others. It will just be that different people will find different parts harder than others.
I want good nutrition/sleep/heavy exercise to benefit me
Good. Get a nutritionalist, see a doctor, join a gym. Martial arts may give you some of this, depending on the school, but it is not common to get any real depth of knowledge in these areas. So if these are important to you, see the specialists in these areas. Just like you wouldn't ask your personal trainer how to defend against a knife-weilding assailant, you wouldn't ask your martial art teacher about your sleeping patterns.
I do NOT want to be whacked in the head a lot - I like my brain.
Okay, a few people have mentioned Kyokushin, and while it is true that head punches are disallowed in competition (not in the street, see above re: competitive versus self defence), head kicks are. And Kyokushin practitioners do have a habit of not protecting their heads because they are not expecting to be punched there, and as a result, head kicks often result in knock-outs (when they connect). So getting knocked in the head is still a very real possibility there.
To avoid getting your head knocked the most, look to non-competitive systems, grappling systems, non-contact systems etc.
I'd prefer it require some agility.
See above re: gym. See also: yoga or pilates. In terms of a martial art requiring agility (and I'm going to assume that you are refering to flexibility here as well), most that are going to be based in competition will have that, most that are concerned with self defence will not. Just so you know.
I like competitive weapon fighting.
Okay, we're going further away from real self defence here again. A knife fight where both people draw blades rarely continues on to violence, with both people realising how bad it could get and withdrawing. So an idea of weapon versus weapon is rare, except from historical and military settings.
If I could find an art that gives me relevant self defense with the fist or throws and takedowns, and some weapon aspect, I would love it.
Taking out the competitive aspect (as you have here), look to Ninjutsu schools (Bujinkan, Genbukan, Jinenkan), but ensure the teacher understands the way their art needs to be adapted for modern streets. If they say that you can simply train the old movements and be able to defend yourself, they probably need a little education themselves. Also look to Krav Maga, RBSD systems, and others of the same ilk.
But a word of caution. A common claim to enhance a particular schools appeal when it comes to street defence capabilities is to mention the military, security, or police training involved in either the instructors history or the current student body. Just be aware that the Military, Security, and Police all have very different requirements to street defence. The previous mentioned groups are all required to engage in conflict, and move forward, with the Security personnel needing to subdue and remove (little to no striking, heavy on grappling, operating in groups, some minimal weaponry), the Police need to subdue and restrain (similar to the Security, but with restraints due to legal issues. Often a little better armed, but not always better trained - and the Security industry is not the greatest trained by and large, anyway), and the Military need to engage an enemy, often with deadly force (quite a bit different to street self defence, where if you apply the military approach you go to jail).
To cover you latest post here, if you are looking for sparring in terms of two people squaring up, and both trying to attack each other at the same time, please be aware that that is not how assaults happen, so it has no relevance to self defence. Krav Maga, being an Israeli Military system, has no real need for such drills, but will engage in free-form drills where a defender defends against one or more attackers who may or may not be armed, and are restisting. This is a graduated process, by the way. And the way to tell if it's a good school is to visit it and check it out.
I'll finish with this. DO NOT CHOOSE AN ART!!!
The most important aspect is not going to be what system you study, it will be where you study, and who you study with. Visit as many schools as you can/want, check out the instructors and other students, and go with the one that matches your personality the best. You may find that it is exactly what you were needing, even if it is not what you thought you were looking for.
