For the prevention of migraines I take metoprolol. It's a beta blocker primarily used to treat hypertension, and because it is a tension reliever, once enough builds up in your system, it can help to keep you migraine free!
When I'm actually in the middle of/trying to prevent a migraine from becoming debilitating, I've been prescribed fioricet (please note I take the generic form of these drugs but they work exactly the same!) Fioricet is basically just super strong Excedrin migraine. It's got butabital, aceaminophen, and caffeine. No idea what butabital does on its own, but this mighty pill has been a lifesaver when the migraine starts.