Found this on the Web. Tried it. AWESOME.
Goes well with crab, lobster, shrimp, and pretty much all the fish I've tried. It's got a heck of a kick, so it's not for the faint of heart:
1 cup mayo
1 teaspoon capers
2 tablespoons finely chopped green onion
1 tablespoon finely chopped parsley
1 dash (aw, hell, 1 tablespoon) tabasco
1/3 cup Chili Sauce (I recommend Siracha brand)
1 tablespoon horseradish
1 1/2 tablespoon creole mustard (if you can't find that, just use Grey Poupon)
1 dash ketchup (more for color than anything else, and a hint of sweetness)
salt and pepper to taste
Mix all ingredients, store in refrigerator overnight (ideally) before serving.