After playing to the end of the demo I noticed while trying to organize my full inventory that it is possible to duplicate items while scrolling with the mouse wheel while 'holding' a weapon.
http://www.youtube.com/watch?v=F2VEfq_gtsQshows the bug in action, also showing odd behavior of duplicated stacks of ammo, there is more explanation in the video description if it is required.
Sorry about the horrific video quality, I really should play around with the encoding process a bit more.
