An AvGas truck with about a 500-1200 Gallon capacity. Jet-A truck with about 1500 gallon capacity. Sell Premix to keep it simple. A hangar with the ability to hold whatever aircraft your field can handle. The FBO I'm at doesn't have a hangar and it kills our business when the weather gets nasty. A lav cart. A good tug and 28V GPU that run no matter what. Towbars for whatever aircraft you may see.
Now for the facility itself, this is what I look for: Friendly staff, comfy lounge/lobby with cable, some sort of weather service like WSI or Meteorlogix, vending machines, and a reliable courtesy car that I can make a run to the local burger place with.
That's pretty much the extent of my list. I would rather have what I need and not the extras that bring rediculous fees like Signature charges. Then again, I'm just working through my ratings and the costs of those extra fees comes out of my pocket. Some day when I'm flying Joe and Jane Richpersons around in their G600
those costs won't matter so I'll prefer the extra TLC.