Ok, I gave this some measured thought. And I came up with my five (although my answer might be different tomorrow
Salt - what can you say?
Garlic - incomparable richness, can make it mellow, can make it in your face.
Lemon juice - buncha ways to impart acidity, and not to diss the various vinegars, but lemon juice has the citrus quality.
Bacon - again, what can you say? Fattiness, with the pork component. Works in salads, soups, and anything else.
Smoked paprika - OK, this one is a bit trendy, but I am totally enamored with it. Easy way to impart a smokiness and depth of flavor without effort. Magnificent.
Those five can generate spectacular results in any dish. HOWEVER, six ingredients would have added the ONION! Cheese of all sorts is next.