Disclaimer: Please understand that this is a plastic toy meant for cosplay. We do not endorse or manufacture weaponry. It is a gimmick for a game and should in no way be used as a weapon.
This is a functioning hidden blade prop from the game Assassins creed made of entirely plastic. Some assembly recurred
Assembling is a bit of a challenge but I'm sure assassin's creed fans would know a lot more about it than I do. I haven't yet seen it in action but there are some videos on Youtube that make it look "unreal".
This is an example of themed movie or game props, figurines or models available to fans of any kind. 3d printing is an outlook for many prop artists and designers.