Best chance:
French, art, geography, English lit & lang
Serious study required:
Biology, physics, chemisty, maths
Chemistry is my most forgotten subject. Maths was my hardest. Living with geeks, some parts of physics come up as "light dinner conversation" so some topics are better than others. It took serious revision to learn the 30 equations for my paper in the mid-90s though. Biology was my strongest science.
My era was mid-90s. About 75-80% final exam, no modules.
English was open book at GCSE & A-level, but to have time to write, you had to know what exactly you were looking for and where in the text.
I'm not sure if facts stick as easily as they did 30 years ago, and my geography case studies would be outdated, but my understanding of terminology and processes is still strong.
Duolingo has helped me retain my French and build in other languages.