3. Ulysses (New Vegas)
One of the more controversial and divisive characters in the Fallout world, Ulysses was a courier for the Legion prior to his very strange disappearance, and nearly dies during the game when several nuclear warheads are detonated. This set him on a path to change America, one which outlines him in many ways as the conscience and the soul of New Vegas' story (and depending on how you act, even more so than the player themselves). Ulysses is obsessed with killing the Courier, due to his belief that it was the Courier's fault that the Divide was destroyed. As the only non-mutated survivor of that catastrophe, he's the only one who seems to really maintain both his humanity and sanity, hence his crusade against us seemingly genuine and far from black-and-white villainy, as is too common in gaming. When you eventually meet Ulysses, you can either kill him or convince him not to kill you. Though we haven't a clue which one will be canon, seeing Ulysses' unique brand of philosophy would add the requisite intellectual dimension that these games need.