Grandmama? LJ? I think Shaq would make a great cop. He already knows Shaq-fu, so Chinatown would be great for him. (Of course, I say this just wanting to see what a bunch of angry Chinese men can do against a 400 lb monster.)
If Shaq is really into being a cop or security officer, the best job for him, imo, is to become a body guard. Try to imagine if he was the body guard for KB, KB would have no trouble at all now.