Modder iCE La GlacE has created iCEnhancer 1.2, which not only brings high resolution textures, car models, and diverse new visual effects, but introduces a zombie survival mode as well. If that weren't enough, the AI has been improved as well, allowing NPCs to commit crimes and give them the ability to carry bodies.
At some point, Rockstar will have to take notice of this modder and give him a job.