Propranolol
"I was suffering from migraines for over a year before I sought treatment.  By then I was having one every other day.  The day I didn't have one, I was washed out and drained.  Within a week of starting propranolol, my migraines were gone.  I haven't had a single headache of any type in two months.  I also haven't had any side effects.  Well, until today.  Not really a side effect though.  I missed three pills and started getting dizzy, nauseous and headachy.  So it's actually a side effect of NOT taking my medicine."