German!
I took German for A Level and loved it! Also took French for GCSE, but decided to stick with German for A Level. Started learning French from year 7 but German from year 8, and I can honestly say that I found German a lot easier than French - it's a lot more logical, when it comes to things like cases, word order, genders, and grammar in general. My teacher had a theory that if you were good at maths, and had a logical mind, German would suit you better than French, and it proved correct for everyone who was in my German set for A Level - all of us took Maths to at least AS.
EDIT: Oh, and I also intend to carry on studying German alongside (on top of) my course (hopefully to C1 or C2 level by the end of the course).