Traditionally, one would probably tell you that you need a science degree to be the most competitive.
In reality, pharmacy schools are looking for well-rounded individuals who will fit in well at their school. When you submit your applications, you want to stand out (in a good way) from the rest of the "typical" candidates. Having a degree in a non-science field may actually help you stand out. I've heard of art majors, English majors, and even communication majors being accepted at schools. They're unique and they can bring something different to the program that a class full of biology majors may not be able to bring. Not to mention, just having a 4 year degree by itself increases your competitiveness.
If you do well in most of the pharmacy pre-requisite courses, have a good overall GPA and have some work and extracurricular experiences, you can probably guarantee that you'll get accepted somewhere, regardless of what your degree is in.
I was accepted with a degree in health science. (Kind of a mix between science and non-science.) If pharmacy didn't workout for me, I wanted something other than biology or chemistry to fall back on. I did take a few upper division science courses and I earned a minor in a science, just to make me a little more competitive and to show that I could handle a tougher science curriculum.