The most basic and important human right is clearly the right to life. If a person does not have this right, nothing would really matter. Apart from this, I would say that religious freedom would be the next important human right.
I say this because religion is bound with our consciouses. We, as people, have convictions and we should be able to express them freely. Moreover, we should allow others to express their religious sentiments freely as well.
Another reason that I choose religion is because it shapes a person's worldview, relationships, feelings, meaning in life, and much more. In other words, religion is all encompassing. Perhaps an example will help. If a person is an observant Jew, then his or her entire life would be shaped by his or her religion - diet, education, use of money, marriage, and so much more. Without this freedom, life would be severely limited.