If I have them from a fast food outlet, I just sprinkle pepper on them and eat them like that. If they're thick and wedge-cut, then I either prefer them with cream gravy (if I'm having them as part of a chicken strips meal from one of my favorite local eateries) or mayo (if I'm having them at home). I got the mayo idea from watching a TV show about "fries" (what we call "chips" across the Atlantic) and seeing that the Belgians, who originated the recipe/cooking method, dipped their pommes frites in mayo or mayo-based sauces. So I figured if it was good enough for the people who invented them, it was good enough for me.
Although -- I can't resist sprinkling pepper on the wedge-cut potatoes. This would be freshly ground black pepper, BTW. When they're straight out of the oven (because I oven bake them if I'm having them at home). And then a little salt, i.e. enough to give them a little flavor. Oh, and leaving the skin on is imperative.