Tartare sauce is awesome for fish and potatoes (mashed/boiled). I love it more than any other sauce, but only really when used on those two things.

Cheese sauce is awesome for vegetables, particularly cauliflower and brocolli.

Mustard sauce is awesome for corned beef, if that's the sauce that you have with corned beef. I think it is.

Tomato sauce is awesome on any red meat or chips.

Chilli sauce is awesome on anything that suits chilli sauce.

With these five sauces, along with gravy and dips, you can compliment almost any food in the world.