If they're restaurant chips (which tend to be quite dry), I just sprinkle a little salt on them.

If they're (Fish &) Chip shop chips, which are more greasy, then with lashings of salt and lashings of (malt) vinegar.

If it's McD's fries we're talking about, then I usually pick up a cup of BBQ or light curry sauce and dip them in that.

If they've come as part of Sausage, Chips and Beans, then I either put a little Ketchup on them, or eat them with the beans.

If they've come as part of an all-day-breakfast, then definitely ketchup, although dipping them in the egg yolk is good too.