No Halloween costume this year, but I did recently make a prop for a friend. Behold, a cardboard replica of the M41-A pulse rifle as seen in the movie Aliens...sort of. In my haste to finish it, there are some minor details I forgot, like the black clip things on the magazine, but overall it's pretty accurate. A miscalculation on my part made the grenade launcher bigger than the original, but I think it makes it look more bad-ass :) I regret not taking pictures during the process, but I am mighty tempted to build another one for myself because it's so freaking cool to hold one, so keep an eye out for a full Instructable later on, though probably not before spring.
The prop is 95% cardboard, built on a 1:1 scale as best as possible. Triggers were made from plastic clothes pins and can be pulled. The magazine can be pulled out and holds in place when pushed back in. The loading bolt can be pulled back (made from a toilet paper roll holder), opening the shell ejection port. The grenade launcher can be pumped back to open the loading port. All in all, it's pretty much a fully-functional toy.