some use a dash of nutmeg even.
i add a little english mustard powder (or dijon at a pinch) and some cider or white wine vinegar. i also use the SHARPEST cheddar i can find in the US -- the vintage tillamook cheddar is my current fave. my dad made it every saturday while i was growing up, and always went on about the secret ingredient that he'd never reveal... finally once i'd left home, he admitted it was nothing but some extra TLC (tender loving care) for us.
no matter what i do, DH insists on adding tabasco sauce to it
. one time he did convince me to split the cheese 50/50 between cheddar and pepperjack, and i have to say, that was pretty nummy.
my mac & cheese cheat is to toss boiled noodles/pasta in mayonnaise, ranch dressing, and grated cheese. but that's just for me -- not DH or DS. i don't know at what point it stops being just mac and cheese, but i also throw peas and franks/wieners in there for comfort food.