When we think of the most important parts of the Torah we may think of the aseret hadibrot, the shema or the mitzva to love your neighbour as yourself.
These sections of the Torah are most noticeable and given with much fanfare; the discussion between G-d, Moshe and the Jewish people as they prepared for Sinai, the call to holiness and the gathering together of the people as the ethical centerpiece of the Torah is detailed, and the call of monotheism and our love of G-d.
Yet one could argue that the most important mitzva of the Torah is to sanctify G-d's name with the most serious sin being the desecration of G-d's name. Actually it's not much of an argument as all seem to agree with its central importance. It is the only sin for which Teshuva in this world is not possible (see Rambam, Hilchot Teshuva 1:4). The mitzva of sanctifying G-d's name is so great that at times we are called upon to sacrifice our life so that we may sanctify G-d's name. The Gemara in Yoma (86a) subsumes the mitzva of ahavat Hashem, loving G-d, as part of the mitzva of kiddush Hashem. Loving G-d, the Gemara notes, means causing others to love G-d and that is the essence of sanctifying the Name.
And yet this mitzva is "hidden away" and I suspect that many who know exactly where the aseret hadibrot, the shema and love your neighbour are recorded would be unsure where to locate the mitzva of kiddush Hashem.
It is found in the middle of a series of laws dealing with animals; when they may be sacrificed, when they may be killed, and when they may be eaten (Vayikra 22:26-33). Despite the concern we must have for animals it seems like a strange location for a mitzva the essence of which is modeling a relationship between human and Divine, a relationship totally absent from the animal kingdom.
While I do not fully understand the Torah's placement of this mitzva perhaps this is in keeping with the Torah's style of often presenting mitzvoth where we least expect them and where we might have argued they do not apply. Thus the mitzva of how we are to treat our spouse is recorded regarding a slave and that of a proper and speedy burial is recorded in the context of a convicted murderer put to death. In fact much of the honour we must show others is derived from the honour shown to the deceased. Imagine how much more respect we must show the living!
The mitzva of kiddush Hashem demands that we be conscious of our divine image and the image of the Divine at all times. And we can see the true character of a person when we are free to act as we like and there is little holding us back. It is in how we interact with the animal kingdom that we can best demonstrate that G-d's "mercy is upon all his creations."
The fact that we must wait seven days after birth before offering an animal as sacrifice, nor kill an animal and its offspring on the same day and ensure a thanksgiving offering is eaten on the day it was brought serves as a model for much more than the animal kingdom. They teach the importance of time, our most precious resource. We should not be surprised that immediately following the mitzva of kiddush Hashem the Torah details the laws of the holidays, the days on which we sanctify time.
Yet there is much more we can learn from the animal kingdom; "Rav Yochanan observed: If the Torah had not been given we could have learnt modesty from the cat, honesty from the ant, chastity from the dove, and good manners from the chicken." (Eruvin 100b)
If "timing is everything" then using it correctly is the essence of life. It is not just what we do that matters but when we do so can be equally important. Acting in a proper matter in the proper time is the essence of kiddush Hashem. Shabbat Shalom!
 While we are all taught at a young age that the three mitzvoth for which we must suffer martyrdom are idolatry,adultery and murder such is not fully accurate. In truth the reason we must chose martyrdom is because of the mitzva of Kiddush Hashem. One who for example converts to another (idolatrous) religion undress duress - like many did over the years - is not considered to be violating idolatry. He converts not because he believes in the other religion but because he wants to save his life. It is the mitzva of Kiddush Hashem that has been violated. And that mitzva requires we give up our life for these sins and - and this is not as well known - if the sin is done in front of ten people or is done even privately in a time of general religious persecution.
 The commentaries debate whether the mitzvoth relating to animals are for the benefit of the animals or to inculcate positive traits in humans. "An ox and its offspring you shall not kill on the same day." Is this because of concern for the feelings of the animal or is such an act cruel for a human to do? These need not be mutually exclusive. In any event our sensitivity towards animals must heighten our sensitivity towards human beings.