This is incredibly subjective.
I've seen a lot of people put down English Lit as the hardest, whilst I found that i needed to revise Psychology a lot more. Maths took the biscuit for me though.
Imo;
Maths, Biology, Chemistry and Physics.
History, Geography, English Lit, Psychology and Languages.
Sociology, Economics, English Lang + Lit and Philosophy (although Philosophy could be in the above bracket too)
Music, Media, Business studies and RS.
Government + Politics, Accounting and Art and Design.
Photography and Film studies.
No idea where ICT, Law and several others fit in, though.
However as I obviously haven't studied every course, I'm relying on other students opinions, and who got what grade in what A-Level.
Feel free to disagree.