After becoming a Big Daddy, don't go into the training area. Splicers elsewhere now don't even notice you. They walk right by. You can do anything. Run up to them and murder. As long as they're unprovoked, or not scripted attack Splicers, you can do anything. Go to Medical Pavilion and keep pressing the switch on the door you get the key for with Telekinesis, then kill all the enemies in the water. It's fun.