mostly in the form of backing Superunknown.
The berserkirs were not only a select group of warriors, but to some degree alien within their own culture.
Going berserk was eventually outlawed, as it became practice for men versed in it to instigate fights from which others could not back down nor substitute with champions - and by this the rogue got himself property and whatnot.
The ancient tradition of it is embedded in mythology of Wotan - the god whose role as psychopomp (cognate with Hermes) evolved into the induction of battle rage through magic (or drugs, as most scholars see it), and realm of death that all soldiers must reconcile themselves with.
Some trace the etymology of the word berserk to the word bear (or bear-shirt), and the obvious implication is that the bear's reknowned ability to continue it's carnal rage long after receiving mortal wounds was a magically property that could be spiritually infused into the warrior whose totem and practice was the "bear".
These guys were the original leathernecks, there's no doubt.
Personally, I'm not too concerned with the weapon they're depicted with. It's my understanding that there was no single weapon emblamatic of these warriors. The paucity of iron among the scandinavian people of the time meant that they traded for many weapons - and so I'd imagine that they'd use whatever they could get their hands on.
One last side note: the German civ should get this unit too, IMO (they do in my mod, as do the Russians).
. (It was in the Axe episode of "Conquest" BTW 
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