Are there any conditions which make oneself completely unredeemable in the eyes of God? I am curious if there are any actions or conditions which "seal your fate" so to speak, such that should you do them—no matter how much you repent or accept Jesus or pray—that you are doomed forever to Hell.

For example, Richard Dawkins wrote several anti-God books and has long been critical of religion; is it possible that he's "passed the threshold" of "saveableness"? Or are we all always saveable? Or someone who is born gay, and while I understand not all Christians think gays will go to Hell, there are certainly some major groups that do. Are these people then, genetically determined to go to Hell? A better example might be someone who is born blind and deaf, or extremely mentally ill, such that with no amount of instruction would they be able to understand the Bible, let alone the concept of "book" or "savior". These people would never embrace Jesus; are they damned from birth without any hope?

In other words, is it possible that the conditions of your existence could doom you to Hell inevitably, despite any efforts or willingness on your part?
Jesus answers this one pretty clearly: such a sin does exist.


  Mark 3:28-29
  
  28 Verily I say unto you, All sins shall be forgiven unto the sons of
  men, and blasphemies wherewith soever they shall blaspheme:
  
  29 But he that shall blaspheme against the Holy Ghost hath never
  forgiveness, but is in danger of eternal damnation.


Unfortunately, nowhere in the Bible does it actually say what constitutes blasphemy against the Holy Ghost, and speculation as to its meaning tends to be all over the place.