Of the subjects I did, probably Astronomy and Business Studies were the easiest. For Astronomy I basically memorised facts (and not that many of them) and regurgitated them; for the coursework I drew a picture of the Moon (much of which was traced rather than drawn freehand) and filled in an observation chart showing its phases over the course of a few weeks. The exam was a complete piece of pi**.
Business Studies was likewise largely memory-based with a handful of longer questions where you had to apply knowledge to a given situation.
Italian, which I did this year, was arguably easier for me personally but that's because languages are my kind of thing. The reading and listening papers in particular were of a standard you might expect of a not-very-bright ten-year-old on the Continent studying English.
As for the people who say maths requires the least effort - yes, of course it's easy if you have a gift for it, but I think if we want to be objective about this we need to assume no particular talents for anything. I struggled with maths no matter how hard I tried; it's a subject where you have to decide what knowledge needs to be applied and use it to work stuff out, whereas with some subjects all you do is regurgitate facts, no actual processing or application is needed.