On a search to find what the heck the spear was that Loki is using in the avengers I came across this guy .
His Name is Perrikus and he is a Thor villain. He is a dark god from a different world and you will notice that He is carrying his trademark spear that has a remarkable resemblance to the one that Loki uses in the avengers.
On on end of the spear it has a 2 pronged head, and in the comics the other end shoots out a magical death ray of destruction capable of destroying anything it pleases, Which sounds a lot like what we saw in the avengers trailer.
So whether or not Perrikus actually appears in the avengers or not, I have no doubt that they just took the two ends of the spear put them on the same end and gave it to Loki in the movie.
Agree or Disagree
find out more about Perrikus at http://marvel.com/universe/Perrikus