Just like in most other roleplaying games, CODE/X character is a resident of the game world and whose role in the game the player is playing. He or she can be anyone or anything, but as a rule of thumb characters in survival horror adventures are survivors themselves: tough cookies who can and will play it hard with the danger. Looking at the movies and video games of the genre, we can deduce that they are typically:

Gordon Freeman (Half-Life 1&2) is really the odd one out: he is an accomplished physicist and researcher. His physical fitness and ability with weapons remain a mystery.

Your character does not need to a carbon copy of any known character or hero, let alone a tank with every pocket bulging with weapons. But he or she must be able to look after herself, or else he will be a burden instead of a benefit to the group.