We had a great co-op scenario that we adapted from a solo scenario, which we originally adapted from resident evil. It basicly entails however many players you want (to a reasonable limit, as we played with betweent 3 and), and each player has 200 gc to spend on a maximum of 3 models.
Once you have done this, you set up a map with a large building in the centre and very little scenery other than this. This building is the 'inn' (or similiar gathering place) everyone sets up inside or near to, so it helps if it is a building that you can access the inside of. One player is the inn staff, the other players are guests and are all chugging back a few pitns after a hard day. But what's that noise from outside...could it be...a zombie horde approaching the tavern?
basicly everyone has to defend the tavern or run for their lives, player's choice. but its a great laugh and you can adapt it in any way you see fit. One game it was a burlesque theatre staffed by sisters of sigmar that the patrons had to defend from an angry mob (think simpsons) but basicly whatever you like.
P.S I apologise for my poor english