[piotrj]

How about NERF guns? http://www.hasbro.com/nerf/en_US/vortex.cfm Those vortex type ones have disc ammo. You can buy them on Amazon.

[andrewflnr]

I'd rather do it with a jolt pistol. The discs have a long range, but they're terribly inaccurate and slow. The single dart fired by a dart is slow to reload, but fairly accurate and fast, perfect for assassinations.