As far as I know (current uni student so talked to quite a few people about GCSEs with regards to university admissions in the past) what GCSEs you have taken isn't terribly important in comparison to the AS/A levels you choose to take. That being said, if you want an idea of the subjects that good universities prefer, it's worth taking a look at the Russell Group's 'Facilitating Subjects' document (it's somewhere online). This list applies to A levels, but if you're really unsure about GCSE choices it's probably worth taking a look at that anyway, you might be able to get a head start/good grounding for subjects you go on to take at A level by taking them now.
For instance, History is seen as a 'facilitating' subject, so unless there is something else you really want to do instead of it, I'd say it's a very good subject to pick (I regret not taking it at GCSE because I think it's fascinating).
As the above poster has mentioned, the number of As and A*s is what really counts (particularly if you can get them in your core subjects: English, Maths, Sciences). I remember being told the average Oxbridge entrant has something like 7 A*s at GCSE after I got to college (thinking 3 A*s was really good haha), so bear that in mind.