The Vicar was resource aggressive when we got him. If you tried to touch any of his toys, or if he thought you would try to touch his toys (or his food, or his treats, or his bone), he would snap and bite (and immediately apologise, but still).
After using the "trade you up" method (where he gets something even better in return), he shares his toys voluntarily. We can also take his food, bones or treats away from him now. It took a while, but it was well worth it.
The Vicar is a Friese Stabij or Stabyhoun, who was 6 1/2 years old when we got him from an abusive past.