I think I mentioned this in another thread (about inventions, IIRC):
cheese, marmite and treacle.
Peanut butter, mayo, and tabasco sauce. I usually have it on a tortilla.
No, no, no!
Peanut butter, mayonnaise, and banana. Mmmmmmm…
At my wedding, my childhood babysitter and one of my college roommates discussed my lifelong fondness for this sandwich.
Peanut butter and Mayonnaise, it is. I just ate one to celebrate this thread. First one I’ve had in a year or so. Must do this more often. However, the pot of Russian borsch is calling to me. I’m ready, I have the marrow bones simmered, the beef meltingly tender and special Lebni yoghurt to float in it.
My current favorite is peanut butter with two Eggo waffles as the bread(flavored waffles, like strawberry or banana bread), but compared to some of these mine doesn’t seem all that weird. 
I am highly allergic to peanut butter - although I don’t think I knew that as a child; I would always refuse PB sandwiches, and was often offered MUSTARD SANDWICHES as an alternative. Yep, that would be bread and mustard.
My 8 year old boy loves peanut butter/banana sandwiches. Viva Las Vegas…
I had a sandwich made with anchovies and slices of tomato at a train station in Spain. It was very good! 
Another vote for the peanut butter and butter. I ate those all the time as a kid. Also, American cheese, Miracle Whip, and pickle relish.
I eat macaroni and cheese sandwiches on bagels or rye bread.
I love fish finger sandwiches. I put three fish fingers on a slice of white bread with mayo, mustard, tomato, and cheese, on white bread. If I’m in the mood, I’ll put a squirt of lemon juice on it as well.
I also like to make tuna salad with mayo, onions, green peppers, tomato, cucumber, salt and pepper and a bit of mustard. I finish this with a slice of cheese. For some reason, this sandwich is considered strange in my house and by many of my friends, but I really don’t see anything wierd about that one!
Oh yes, and I really do like Vegemite and cheese sandwiches.
Ham, mashed potato, mustard and red cabbage (cooked). Can’t beat a leftovers sarnie!
That essentially a steak tartare sandwich. It’s not very weird at all. Tell him to try it without the refrigeration or the bread.
All that peanut butter stuff is mad though.
I eat peanut butter with butter occasionally.
I also eat peanut butter, banana, and bacon sandwiches.
You can have peanut butter with most things as long as you call the sandwich “satay”.
When working in the UK, there used to be a snack shop in our office block where the owner would make the strangest combinations for sandwiches. My Favorite:
Boiled Ham
Beetroot
Slice of Fresh Pear
Stilton
In a Pita
Just plain mayonnaise on white bread. Lots of mayo.
White bread, mayo, banana slices and hammered up peanuts, not peanut butter.
White bread, lots of mayo, 1/4" thick slices of fresh tomatoes.
BLT’s with lots of mayo.
White bread, cottage cheese, banana peppers, tomato slices, lots of ground black pepper.
Peanut butter and banana sandwiches. Actually, they were Elvis Presley’s favorite. However, I tried it once. It was pretty good.
My mother ate EVERY sandwhich smothered in butter. Bologna, tuna, peanut butter. No wonder she is the size of a house!
Yowzah!
My mother once gave my dad a sandwhich and he said “what there is nothing on it” She said it was a “jammed sandwhich”
2 pieces of bread jammed together. I guess that’s what he gets for complaining about her meal making skills.
You can always go for a bread sandwich: three slices of bread.