Faith by definition when applied to God is: belief in Him without proof or evidence of "things seen."
Can you be saved by God or at Armageddon if you do not have faith, or If you doubt God exists? According to JW's and most Christians that is a big fat NO! Lets chip in some analogies to illustrate the ridiculousness of this ideology for a minute.
Imagine back before phones and internet. A soon-to-be father is wrongfully convicted of a crime and sent to an offshore prison for a 30year sentence. His son is born soon after and is raised by his mother to believe that his father is alive and well and will be returning in the near future. This father communicates to his son for 20+ years by letter only and never receives or responds to his sons letters. There are no pictures, old clothes, or other physical evidence of this father for the child to see. Only these letters. In these letters the father emphasizes to his son among other life lessons and 'rules,' that if the son does not believe that his father exists and will return, then when he does return, the father will find and kill his son for non-belief. Of course the son believes out of fear for a while but eventually grows older and reasons that these letters may be coming from his mother or another relative in some attempt to raise him with a father figure this whole time. Thus the son stops believing its really from his father. At age 30 the son gets his throat slit by his returned father for not believing he existed this whole time. Justice has been served, right? Do you believe Jesus/God exists? Is it really necessary to? Wheres the evidence? Is it in some old letters?
I also like the Firefighter analogy in this short cartoon clip: https://www.youtube.com/watch?v=LSZqH0Ms4ds