As found in Akka 2.2-RC1, Scala 2.10.1

1. Create a sample Akka application.conf:

test {
  my-dispatcher {
    type = PinnedDispatcher
    executor = "thread-pool-executor"
  }

  akka.actor.deployment {
    /test-actor {
      dispatcher = my-dispatcher
    }
  }
}

2. Create sample actor and system:

object ActorTest{
  def main(args: Array[String]) {
    val conf = ConfigFactory.load()
    val system = ActorSystem("test", conf.getConfig("test"))
    val ref = system.actorOf(Props[TestActor], "test-actor")
  }
}

class TestActor extends Actor{
  def receive = {
    case _ =>
  }
}

3. Run your code: 'test-actor' will use 'my-dispatcher', as intended.

4. Enable RemoteActorRefProvider in application.conf:

akka.actor.provider = "akka.remote.RemoteActorRefProvider"

5. Run code once more: 'test-actor' will now use 'akka.actor.default-dispatcher'