McDonald's

I can't count the number of times I've gone through here to grab a quick bite on the way to or from an airport. Their service is fast even though customers are from all manner of nationalities travelling and that they're often busy. Plenty of staff on and the food is of good quality. Pretty much always open.
Easily accesible from both International and Domestic. The only negative is there's pretty much nowhere to sit once you've got your food which is a shame.