I think the most helpful rotations for neurology are the following: cardiology, ID, ICU, radiology, and rheum.
Neurovascular, which will be a majority of your PGY2 in most programs shares similar principles to cardiology, and ICU experience makes you a more competent medicine doctor, and teaches you to handle acute situations.
Infectious disease overlaps into every other field, and it is important to learn how to manage UTIs, PNA, and other common infectious. Plus, knowing how to manage medical issues will make your inpatient life so much easier.
Radiology (neuroradiology) is helpful for obvious reasons, but I would also learn how to read CXRs, KUBs, ultrasounds.
Rheum is good for reasons mentioned above. Good overlap with neurology, plus will give you experience in joint injections and immune-modulating drugs which you will use relatively frequently.
Not sure how much benefit heme onc would have, aside from maybe developing your communication skills and dealing with palliative/end of life issues.