I wouldn’t call this an unlikely pairing(s) since both or condiments but a combo that I like to are Ham and Cheese sandwiches with salsa or barbeque sauce on them. I’ve discovered these combos a while back because one day when I was making a sandwich. I realized there was no mustard or mayo, so I figured why not I try salsa on my sandwich. The same thing happened again with no mustard or mayo, so I applied barbeque sauce. The sandwiches turned out great. Salsa and barbeque sauce are both condiments.
I don’t find shame in admitting this because you always need to improvise. If you don’t have time to run to the store always try something new. What’s weird to others may not seem weird to some people. I think our perspective of what’s normal to apply on food is a bit sheltered. I recommend others to try applying salsa or barbeque sauce on sandwiches to see how it taste. If you don’t think it’s something you would want to try, then that’s fine too.