1. Get hit with something heavy, sharp and/or pointy
3. Death from above
4. Get burned alive
It wasn't just arrows that fell out of the sky, either. There were all manner of catapults, ballistae and trebuchets that were exceptionally capable of flinging all sorts of objects over long distances. What was worse? A heavy object falling from the sky that was also on fire.
Now, some thought the one sure-fire way to not die in a medieval battle was to stay behind the solid rock walls of your castle. However, a patient army could camp around your castle and wait you out. This took real patience, though, because sometimes castles had stores that would last them a year or more. Impatient besiegers sometimes threw dead bodies and dung over the walls--the medieval plague bomb--hoping the people inside were dumb enough to inspect these unwanted surprises. Of course, nothing was more embarrassing than showing up for a siege and having to abandon it when you ran out of rations.
See full article at http://www.kindlepost.co.uk/2012/05/five-ways-to-die-in-medieval-battle.html