Just as the title says, really.
We’re having a cold plate supper this evening, including homemade potato salad.
Which got me to wondering, what’s the unexpected ingredient in yours?
Sometimes I add a little pickle juice to mine, and sometimes, very finely shredded snow peas, not too many though.
How about you?
Any/all of the following: hard-boiled egg, onion, celery.
Lemon and pepper seasoning instead of just pepper. My potato salad is a simple affair, with just potatoes, mayo, celery, hard-boiled egg, salt, and the aforementioned seasoning (and perhaps a bit of dill or green onion if I have it).
Contortionists.
Mine is actually a salad.
Lettuce, mashed potatoes, chives and a creamy vinegar dressing, not too sweet. Mmm.
I don’t know how “secret” it is, but I like lots of fresh garlic (grated fine) in potato salad. Mom put dry hot mustard in hers.
I grew up with potato salad using mayo. Went to a barbecue shortly after moving to Seattle where the potato salad was tossed with a vinegar dressing, no mayo. I didn’t like it.
On preview, no offense Flutterby. I think a creamy dressing would be better than what I had.
Potatoes.
Nothing secretive about it, but I use blue cheese. I make an unconventional potato salad in general - more savory than tangy, and more like dressed potatoes than a chunky mash.
My favorite potato salad recipe uses a half mayo & half sour cream dressing; could be reworked to use yogurt. Plus scallions, celery seeds & sliced radishes. I also like a recipe from The New York Times Cookbook–in a sort of oil & vinegar dressing with tarragon.
Although I like egg salad & regard deviled eggs as a delicacy, boiled eggs in potato or tuna salad make my blood run cold.
(The mercury hit 101 in Houston today; time to think of recipes that can be cooked in the cool of the day & refrigerated.)
Dill and sour cream. It’s not really a secret though. If you can’t tell there’s dill in the potato salad, you’re blind and have no taste buds.
I agree egg in tuna salad (or chix for that matter) is too much, in potato or pasta saled? YUMMM!
My mom puts finely diced pieces of dill pickle in hers. She also mashes the potatoes, so it’s less like potato salad and more like mashed potatoes with mayo in them. There’s onion and celery in there too, along with celery seed and paprika and probably some other stuff I’m forgetting. NOM.
I like the idea of celery seeds–to me, raw celery makes the whole thing taste entirely of celery, but the seeds would add a hint of that flavor.
My recipe uses mayo and sour cream too, also a squirt of mustard and hard cooked eggs. I grate the onion so its flavor is there without anyone biting into a chunk of it. I dress and toss the potatoes while they are still warm so they really soak up the dressing.
My aunt used to make a special Fourth of July potato salad with fresh peas added. Man, I loved that stuff! Think I will give it a whirl myself this Independence Day.
BACON!
Okay, maybe that’s not so unexpected, but it’s goooooood. The unexpected, probably couldn’t name it ingredient, is just a bit of apple cider vinegar, along with the mayo, celery seed and other stuff.
I use scallions instead of regular onions, and about half seasoning salt with half regular salt, but otherwise thisis my recipe.
I hate potato salad. I love *this *potato salad.
I’m looking to reduce the fat content though. I hate low-fat mayo, so I’ll try half yogurt instead, next time I make it.
Good idea, because normally the potato salad at any given picnic is otherwise the epitome of bland filler. For some reason most people seem to think potatoes and flavor don’t go together.
Capers.
Cayenne. I like to blow my guests right out of their Adirondack chairs.
I use dijon mustard and it gives it a nice kick.
I also serve it warm (i.e. just when the eggs and potatoes are done cooking) which most people seem to enjoy - i’ve never had leftovers which is sort of a drag because I would like to try it cold. 
Several years ago I made a family cookbook. Here’s my entry for my potato salad, which I think is freakin’ amazing but which I make very rarely since my wife doesn’t like blue cheese or olives:
Olive oil and a bit of cider vinegar for tang, HBEs and chopped dill pickles, celery, onion, garlic, mayo. Smoked paprika on top.