First, a tame one: Peanut butter, marmalade, and cottage cheese.
Further out: orange juice and milk. You have about one minute to drink it before you need a spoon, but in the meantime it is excellent.
All the way out: Lobster and vanilla. You need courage to try that one. Even more bizarrely, it barely matters if you use real or artificial vanilla.
And one from childhood: cod liver oil and orange juice, which meant government-issued cod liver oil, and government-issued orange juice. I don't recommend the flavour, but it DID go down. The combination is so famous that there's a bawdy song written in its honour
(We also got government milk supplied free, in school, until it was cancelled by the Minister of Education, a young ambitious woman named Margaret Thatcher, earning her the first of many hateful nicknames: Thatcher, Thatcher, milk-snatcher!)