a silly question about knives

[B.C man]

I was playing a play station 3 game called assassin's creed. The protagonist in the game uses this small knife to kill people the most, it is like a concealish sort of knife that he side out from his sleeve.

Would you happen to know if such knife exist? what kind of knife is it lol.

 

[Esav Benyamin]

Here's a recent thread on the same idea: Wrist Blade.

Ah, I found my list of some older threads as well:

Spring realese forearm knives - http://www.bladeforums.com/forums/showthread.php?t=510803
Help!! I need advise on a knife prop for a film project - http://www.bladeforums.com/forums/showthread.php?t=509529
Looking for something different - http://www.bladeforums.com/forums/showthread.php?t=501396
forearm mounted stilletto knife, possible to make?? - http://www.bladeforums.com/forums/showthread.php?t=316984