Question: What are some grilling tools that a beginner should have when purchasing a new grill? Additionally, are there tools that are useful for the more advanced outdoor cook?

Answer: 
If you're using charcoal, a spray bottle with H2O can be handy for flare-ups. Otherwise, I think others have the bases covered.
I have a wide, flat knife that can be used as a spatula; I find it really useful. Everything else has pretty much been mentioned, but I would suggest a pair of tongs with decent teeth on them. It's very disheartening when that burger or steak slips out of your grip and into the coals or onto the ground.