A common misconception is that hangovers can only occur after drinking alcohol. This is of course untrue. There are several other things that can cause hangovers.
Getting punched really fucking hard in the head- After experiencing this you will normally have a throbbing headache and the inability to achieve anything worthwhile the next day. I'd liken it to a Rum hangover... unless you get punched by Rowdy Roddy Piper, then it feels like scotch.
Watching an Adam Sandler film from the middle of his career- Normally when you watch an early Sandler flick you feel joy, and you feel content watching some of his more recent films. But if you sit down and watch WaterBoy or Little Nicky you will feel like simultaneously vomiting and shitting everywhere, and your life will feel completely meaningless.
Heroin- Actually not sure if this causes a hangover... but really how could it not?
Dying- Normally when you're dying you experience the same feelings you do when you're hungover. They're basically the same thing, except with a hangover you get over it to do it again. With death your dead. Unless your a cat. Then you have eight more chances.