In addition to personal knives, which were ubiquitous but used only as a last resort, the most basic weapon, available more or less to all, was the common axe. It is important to distinguish between tools made for farmyard use and actual weapons—they were not interchangeable.
At the extreme, the great war axe of the Danes could bring down a horse and rider with a single blow. They were neither difficult to forge nor especially expensive, and thus relatively widely used.
First, helmets (of all kinds, including the cheapest) were relatively common, which is not surprising given the obvious need to protect the head in combat. Second, at least the metal varieties were considered so valuable that they almost never accompanied their owners into the grave.