I took:
Maths
Further Maths
Biology
Chemistry
Physics (dropped this before Christmas because it was way too boring and I didn't want it to affect the rest of my grades)
My hardest subject was always Biology, since you have to learn so much and understand it all and be able to apply it all well, and then the mark schemes are always waayyyy to fussy. I hope I've got an A in it, but I'm not certain lol.
EDIT: This is all at AS level. I'm going to be dropping Further Maths.