Same question from Reddit:
The 7-Up and milk suggestion is new to me.
As someone who doesn’t care for Mayo, I can tell you many restaurants put it on their bacon/egg/cheese sandwiches. I have to be careful to order it without.
They put in on burgers too 
To the OP, I like peanut butter on Swiss cheese.
Reading this thread brought back memories of my student days when we raided the communal kitchen after smoking something illegal. Those were good times…
Angostura Bitters and vanilla ice cream
Mmm, I’ll have to try that. I love cranberry with yogurt, and it’s hard to get enough granberry flavor.
Hmm, I actually do hate potato salad. That may be why I think that sounds nasty. Truth be told, I’m not really a fan of mayo.
Gee, my weirdest was going to be potato chips dipped in chocolate. Y’all have me beat.
I’ve just got to thank everyone here.
This thread makes a great Okay, I Just Gotta Try All Of These! list.
I don’t think it’d count as weird, but I dip carrots in cashew butter.
Was looking for a way to give up my favorite lunch (PB&J), so I substituted carrots for the bread.
We won’t discuss mac & cheese with sliced hotdogs over potato skins. 
I like to dunk plain toast in hot chocolate.
My husband puts peanut butter in grits. He learned that from his father, who also liked ketchup on scrambled eggs.
Huh. Peanut butter & grits? That’s a new one on me. Ketchup on scrambled eggs? That’s pretty normal IME. (I don’t do it – the only time ketchup comes close to my breakfast is maybe with hashbrowns. Maybe. But lots of folks love it on scrambled eggs.)
When I was a kid I sometimes ate breakfast with my grandpa, who dunked his toast in coffee (not hot chocolate). Wanting to be like him, I dipped my toast in my orange juice and to this day, I love the mix of salty/tangy/crunchy/warm/cold. But I try not to let anyone see me doing it.
Above someone mentioned a salad with oranges and onions - I had a version with oranges and raw chopped garlic and some black pepper, but you have to let it sit for a while before serving).
My all-time favorite is carmelized onions and pasta (elbows work well) with copious parmesan cheese.
I like bacon or sausage links cut up in my grits, and that has surprised enough people to make me think it’s not common. I consider grits to be a salt-and-fat delivery system, so it just seems natural.
I also like pimento cheeseburgers, but these are common enough in my part of the world as to make me think they’re not all that far out.
I like to pour M&Ms to fill a cup about a quarter of the way, then fill the rest with ice-cold water and let it sit for a while. Then I eat it like soup. Very tasty. I don’t do it much anymore because you have to use quite a few M&Ms to make it worthwhile and I’m trying to cut down, but I still have it as a treat sometimes.
One that’s not mine: someone in my library system who was responsible for team meetings used to regularly put out a bowl of Skittles mixed with M&Ms. To me, that’s just asking for trouble, but apparently it made sense to them.
(In my mind, I always called them S&Ms)
Ketchup drizzled over cottage cheese (NOT mixed in), with cracked black pepper.
Grape Jelly mixed in with cottage cheese.
Just a little bit of Maple syrup mixed in with cottage cheese.
I like cottage cheese.
If it’s the cheese and hot chocolate, then I’ll have to acknowledge it isn’t my own personal quirk. This is old school Hispanic. I will cop to the malta and milk, though.
That’s something I would never have imagined.
What is malta?
Mayo is integral to a Brooklyn bacon/egg/cheese breakfast sandwich.
If you don’t care for mayo, ask for an extra slathering of butter.
The heart-stopping cholesterol buzz is the whole point.
Dill pickle and pepper jack cheese. The tanginess of the pickle brings out the spiciness of the pepper.
Ever heard of Waldorf Salad? It’s chicken salad but has grapes, walnuts, celery, mayo, black pepper…and chunks of chicken. Instead of being chopped up and blended, its left chunky - at least my version is. Probably not that weird but no one I know has heard of it.