I don’t really agree Ranma is sometimes portrayed as a braggart in fan fiction; using statements such as I am the best (which incidentally I don't really like very much and find annoying when characters say that - for example Wolverine from Marvel comics saying he is the best at what he does and what he does is not very nice) and saying "Ranma Saotome doesn't lose". I can't say conclusively that Ranma has never said things of that nature in the manga, only that I do not recall him doing so (I'm almost positive he does not at least for his martial arts abilities). I do not see Ranma as a braggart; using the definition very boastful and talkative person for braggart and speaking of yourself in superlatives for boastful.

There were several instances of Ranma downplaying his skills that I can recall such as during the first volume when he (technically she) downplayed his abilities and during gym class where he did so yet again. This by Japanese culture is the proper response and it also has an added advantage for Ranma in that it leads his opponents to underestimating him. That really is not the reason though. The main reason I don't think Ranma did so is because Ranma is a very secretive person who hates talking about himself and did not talk about any of his previous battles (most things about Ranma's past we learn second hand), Akane even complains that Ranma never really tells her anything in the manga. If Ranma boasts about say beating Saffron (commonly commenting about beating a god) it would be extremely out of character, since it would be out of character for Ranma to even mention fighting him in most situations.

In the event that Ranma did once say something of that nature in the manga, I'd like to point out that the manga occasionally introduces a trait or piece of information that conflicts with other arcs; such as Ranma developing an inability to play cards which is countered by multiple other arcs in which he can. When there is a conflicting trait, I tend to discount that trait in favor of the one that has more supporting evidence as being my personal canon. This type of error is common in many works, particularly in long works written by many authors like Batman. As for the Ranma manga, it is a comedy so it uses the rule of funny, i.e. being funny is more important than being consistent. I mostly go by the manga, since I like it more than the anime and the majority of fan fiction, but I'd also like to point out that the anime and fan fiction tend to change or exaggerate character traits (not that the manga is entirely free of doing this as well) so it is also possible that people view Ranma as a braggart from the anime or just from other fan fics.

Of course it is also possible, that it stems not from anything Ranma ever said but from some of Ranma's character traits. Such as his competitive nature, dislike of losing, and belittling/underestimating other characters skills.

Things I would like to see more of in Ranma fan fiction
First off I will state that if I want to see more of these things in fan fiction, I should stop being lazy/insecure in my writing and write the damn stories myself. If I do so well enough it may inspire others to do so. That said I am insecure in my writing and lazy, so hence this list (there is some small hope that this list itself will inspire someone to use them).

Second thing I want to say, before I get to the list; I really do not understand why some things become so common in fan fiction, many thing which blatantly contradict the source material, and other things actually seen in the source material, repeatedly even, do not.

1. Ranma reading.
2. Konatsu - He is an interesting character with some pretty cool techniques and I would like to see more fics with him in it.
3. Ranma attempting to be a matchmaker. Ranma tried to hook Happosai and Cologne up, he did hook up Akari and Ryoga, and he started to teach a clone of himself how to pick up guys.
4. Ghosts, Oni and miscellaneous other Kami. There are quite a few arcs that have supernatural creatures in them and they don't appear very often in fan fics.
5. Ranma being money savvy. Ranma does display knowledge on money. I mostly want to see more of this to counter all the fan fics in which Ranma borrows money from Nabiki (which Ranma never does in the manga), fics in which he gets tutored by Nabiki on how to use money (which doesn't make sense to me since he knows she would cheat him, she will recklessly use other peoples money without worrying, and will sell people out) and considering that he was on a life long trip in which he likely had to make do with very little money fairly often and probably had to deal with people trying to cheat him; it just makes more sense for him to be money savvy (he does barter with Nabiki, cons people for discounts, expressed sadness at having to spend money, expressed worry about money, has taken jobs - once explicitly for money, etc., in the manga).
6. I would like to see more fics with healing things like Ranma doing first aid or cpr (both of which he did do in the manga), physical therapy, meditation (also seen in manga both in the form of prayer and while sitting upside down), massages (again seen in the manga multiple times; once even during a battle), pressure points/shiatsu/Moxibustion for their more common healing purposes, teaching (very important to prevent causing harm), etc.
7. Ranma being sarcastic and pointing out the stupidity/hypocrisy of the people around him. Ranmas fanfiction incarnations generally are not very sarcastic whereas he is pretty sarcastic in the manga.

WTF? Ryoga HAS to be a piglet. BLASPHEMY!

Dragon Ley Lines
This is the essential basis for all of the more complex arts. The basic concept of Ki energy is that it's all around you. It shapes you, molds you, makes you a part of everything, it flows through you to everything around you. The air you breathe, the ground you step upon, the fluids in your body, the fire in your spirit...they're all the same thing, just different expressions. However ki is so much more than that. You think the world is made of Solids, Fluids and Gasses...but they're really all one and the same thing! You keep thinking there's a separation. Warriors draw on it every time they focus their battle aura. It's not just all around you-IT IS YOU! You are energy expressed in form. If you want to change the direction and flow of that energy, you simply change its expression. It's all a matter of will and mind. What makes a hand strong enough to shatter wood or stone? Kinetic force? No! It's believing that you can shatter them, that the energy within you is stronger than so-called inanimate matter. Will and Intelligence are what separate us from mere objects.

The key isn't belief or understanding or some silly theory about how the Universe is made up; it's knowing what's there that counts. You've got to see for yourself, to let go of preconceptions and even your thought, to learn to react on an elemental level without doubt or hesitation. You already do that for a lot of things you take for granted because you do them so often they become second nature. In order to learn to do new things you have to expand your awareness, let go of your expectations and just do the thing that comes into your mind. Do them with your heart and soul as well as your head.

What we see with our eyes are nothing more than objects and forms, mere reflections of light that inform the brain of their existence through electrochemical interaction. In reality you are not seeing them at all, merely receiving sensory information that formed an audio-visual pattern in the mind like a reflection of the world inside of a mirror. Mere sensualism is not a proper way to describe the harmony of the world, nor could it tell one of it’s living essence. They are not quantifiable things, and as ineffably qualifiable as they are their value to the individual are not the same thing as their value to the Cosmos. You must look beyond the form, beyond the impression to the reality that underlay them. It was all just patterns of energy, some set into frames held in place by a careful balance of opposing forces, the yin and yang of existence. They exist independent of one’s awareness, and yet are far more than the average person perceives.

True warriors must look beyond their frame, look deep into themselves and finally began to see the complex network of energy matrices and force lines that fill the air like waves of heat or magnetism. When the warrior has reached the point where they can see that much, then they can tap into that energy as an external source for their Ki. But the energy already inside them is nearly as infinite. If one can learn to tap into it, then they can harness the Dragon. The Dragon is the mightiest of all creatures. It can soar above the world or engulf it; it encircles everything and is so vast it consumes its own tail. Energy that flows through Yin and Yang makes up everything in existence. We ourselves are the result of opposing virtues that balance us out between the extremes of hot and cold, hard and soft, past and future. Good and evil though has nothing to do with it. Good is the balance between extremes that lets us live in harmony with nature. Evil upsets this balance and causes anarchy and destruction. Everyone has their own balance of light and dark, and some are more balanced than others. If you learn to sense a man's harmony you can tell a friend from an enemy, a casual acquaintance from someone who is trying to kill you. Thus it can serve both equally; energy is beyond human morality, being the essence of the Gods. Good and Bad are the degree to which this energy affects us. For example, someone with the intent of doing you harm upsets the balance if we have given no provocation. You can use that imbalance to your advantage, letting his hostile intent create an opening that you can exploit. The same holds true with gods and demons. All creatures have their own standards for behavior based on need or desire. If you conquer your own desires, then your needs will be that much easier to satisfy and your will can be an invincible weapon.

As Above So Below
A simple exercise in harnessing your ki. First and foremost become aware of your environment. Feel the ions of energy in the air swirling all around you. Feel the wind in your face, feel the sun when it beats down on you and feel the rolling of the oceans, restless and eternal. On land it will be the ground beneath your feet that you may draw upon, but the principle is the same wherever you go. Just chant the phrase, "Sky above, Earth below," and feel the elements reaching out to you, filling you with their ki. Think of yourself as surrounded by a globe of light that is build up from this ki energy, then draw that light into yourself, concentrate it in your body and awaken the Snake that coils within you, the power of the Dragon. The world itself is the Dragon...the sky above is the Dragon, and the sea too is the Dragon. It is everywhere, it is in everything, its breath is the flame of life itself, and its thoughts are as the Lightning. Merge with the power of the Dragon, become as Dragons yourselves. Be young dragons emerging from your shells, stretching out to test your wings as you grow and mature beyond infancy to adulthood. The Dragon will guide you...it is the Worm that encircles the Earth devouring its own tail, and it coils within the base of the spine, ready to leap out and strike at a moment's notice.

The Path of The Sword and Serpent
The serpent is ki or spirit that coils like a snake within you, it represents your spiritual essence and potential. The sword is the mind and will. It is the weapon edge of the self same power. the dc and ac current or positive and negative polarities that are flowing throughout you at every single moment you are alive the head of the serpent is the sky the tail is the earth and the power flows from head to feet and back again. the same with sword it can be thrust upward or downward depending on the direction of your will through ideally the power flows both ways evenly its a matter of polarity as above so below the higher and lower nature operating as a perfect reflection of one another just think of yourself as a serpent coiling and ready to strike or a dragon if you will and the sword of your will to be directed where you aim it.

Looks like Nabiki has great plans...

Ryouga...

The king is gonna fall...

RYOUGA!

Ryoga... won?

Poor little Headmaster ...

And again, Ryoga will lose...

Konnichiwa! Indeed

Wow, quite a good plan...

Mousse kill Raven? No way...

Well Nabiki, you sure seem smug...