First, let's settle the background.
We're in a middle of a virus-induced zombie apocalypse. Infected people don't return from the dead, but have their brain capacities cut to a basic minimum and their only urge; eat humans, and only humans. They will grab, they will bite.
The virus will suppress any survival instinct, pain or fear from infected people. Meaning they will chase you until their heart can no longer feed their muscles and brain, no matter how badly they are injured (broken bones, vital organ failure, muscle tears...).
So two options to kill them: brain injury and bleed them to death.
You are a survivor but you have a very hard time dealing with these starved zombies and merciless thugs. You choose to take a dog as a companion to help you to survive.
QUESTION: What breed would be best suited for this environment?
It would need to be able to spot enemies
Very good hearing and smell.
- Bonus points if it can find food, water and drugs.
It would need to be intelligent
Can a dog understand the concept of stealth? Is there a breed that can just freeze when it spots enemies and doesn't just bark at it?
Would it be possible for the dog to find a secure path by getting around troubles?
Can you give it a mission, like staying close to your injured mate in a secure location while you go outside to look for a first aid kit?
- Bonus points if it can hide itself during a gun fight.
It would need to be able to injure a zombie
Since dogs are invisible to zombies, that would be a very good way to bleed to death an isolated zombie.
- Bonus points if it can aim for the throat.