Whatever you'll actually do well in. There's no "pre-med major" that gives you an admissions advantage — admissions committees care that you handled your required coursework and kept your GPA strong, not whether your diploma technically says biology.
Biology and biochemistry majors do overlap more with MCAT content, which can save you some review time later. But humanities, engineering, and computer science majors get admitted every single cycle, and a less common major for a med school applicant often makes an application more memorable in a stack of a few hundred nearly identical biology majors.