Rigged gun: At first I thought it was a gun which, through a menu, took the shape of any gun. That way you could kill someone with a shotgun and then swap to your "scout" and get away. Then I realized that would remove one of the greatest parts of detective work done by then innocents, and that this isn't even your idea. Your idea ended up being retarded.
Cloak: A cloak isn't a bad idea. I remember in Modular Combat that cloaked players could be seen if someone shone their light at them. The episode 2 shadow was never disabled so you saw this shadow. It was pretty cool.
Tazer: If you can get close enough to use this and kill them with your gun, why not just kill them with your gun? Seems redundant.
Suicide Bomb: No.
Manneguin: ....no.
Grenade:
I don't really like messing with people's vision or controls. The flashbang is the most hated weapon in CS for a good reason (see also: Valve nerfing TF2's Sandman stun).