The apple is a prominent symbol in christianity representing the forbidden fruit and consuming it representing giving into temptation.
In Death Note the apple can be seen in a similar manner Ryuk, a shinigami or god of death, even compares an apple to a shinigami being the equivalent of cigarets or alcohol to humans.
The Death Note itself can be interpreted as a stand in for the apple or rather a forbidden fruit. and using the death note the equivalent of giving into temptation.
Light even makes the statement that there is something about the Death Note that makes people need to try it just once.
There are five rules written on the inside cover of the Death Note explaining how to use it. While not a direct parallel to the ten commandments they are a list of rules written by a god and handed to a human.
Throughout the series Light grows a large following becoming known as Kira the saviour. The religious following that supports him can be interpreted as either a new religion being formed or a dangerous cult.
There are those within the organization which are reminiscent to modern day televangelist who appear on television claiming to speak for Kira, their god, asking for money to build churches in his name and convert others to their faith.
Names in Death Note are very symbolic, with the main character Light Yagami's name being the most significant.
In japanses his name is written with the kenji for night and god. However from a Christian perspective a character named Light, who wishes to bring in the dawn of a new world, is reflected more of Lucifer. In latin Lucifer can be literally translated to "Light Bringer"
this is not the only parallel to Lucifer seen in the show.
This youtube video does a good job at identifying christian symbolism within the first opening of Death Note.