BIG ups to Pat above for the Lawrys props.
I've tried any manner of substance on "french fried potatoes" or "fries" as you call them.
Ketchup
Standard American barrel mustard
Brown mustard
sweet dijon mustard
spicy dijon mustard
mayonnaise, both Miracle whip (ugh! EW!), Kraft (getting there) and Hellman's (MMMM! Now we are talking!)
sweet bbq sauce (like kc masterpiece)
savory bbq sauce (like Kraft original)
A1-sauce in various formats.
Various and sundry hot sauce (cayenne based vinegars, sweet based peppers, all sorts)
Ranch salad dressing, blue cheese dressing, french dressing,
Liquid nacho cheese
shredded cheddar
Jalapenos, jalapeno (juice) from pickled jalapenos
Chick-Fil-A Honey Roasted BBQ. I dunno for what that stuff is originally intended, but damn its good.
Mcdonalds bbq from nuggets, hot mustard, sweet and sour. McD's honey mustard is not palatable.
chili both with and without cheese. Differing variations too from award winning BBQ event chili (at the chili cookoff) to Hormel chili no beans.
Favorites - honestly its usually plain. SOmetimes a vinegar based hot sauce like tabasco and dipped in ranch dressing.