Chip shop - curry sauce or gravy.
Home cooked - if I've made them myself, just salt and vinegar, if they're bought, Maggi's hot and sour sauce, or Hellman's.
Everything. Seriously, I'm not kidding. I could eat a plate of chips smothered in cheese and covered with mayo, ketchup, brown sauce, sweet chilli sauce, mustard, vinegar, the works.
If I had to pick one, I'd probaby go for mayo, a la Amsterdam.
I eat chips a lot, at least 3 times a week and rarely have them with anything other than salt & vinegar. But on that rare ocassion that I do, it's gotta be mayonaise.