so I am a little confused. When you say "specialize", do you mean you undergrad major or medical specialty? (btw you cannot narrow down med schools till you take you mcat. Sorry, but it is just too naïve).
Anyway, I will answer both
1) If you mean undergraduate major, - seriously, do whatever you want. I have classmates that majored in philosophy. LIterally. I was biochemistry, and I felt like that helped me a lot . So if you are thinking "science", biochemistry is a good one. But really - use your undergrad time to specialize in what you want. Think if this is a great time to be brave and explore.
2) if you mean medical career. I do not mean any disrespect, but slow down, tiger 🙂. First you need to take MCAT, - I do not care how well you are doing in your first year classes. Till you take MCAT you really cannot gage your competitiveness. Secondly, don't even think about your specialty till you get into medical school. Personal biased opinion - I cannot stand people who go in without experience and say that they want to be a surgeon, or something else. You know NOTHING at this point. The only time when I will believe it is when you are non traditional and you were an EMT, for example, and you are saying you want to be an ER doc, or something similar. Basically, when you have a long term exposure to a closely related career. Anyway, - get to medical school, and be open minded. Your life will be so full of various medical experiences, and honestly, in my opinion, if you just tell people that you are not sure and you want to be open minded, - to me it shows that you are acting like a responsible mature adult. You are not rushing into decisions that you wont make for SEVEN MORE YEARS!!!!
anyway, good luck!