Originally Posted by Brian McIlmoyle
If you respond to a false threat.. and move from your position.. you deserve to be shot.
it's exactly the same as not permitting feints in a boxing match.. the purpose of the feint is to draw someone out of their guard to respond to an action that is not a threat so that a real attack may now be launched to the exposed area. Perfectly legitimate and valid combative technique.
I'm kind of split on this one. I think that Brian's point is correct; disruption tactics are an important part of the game. You don't want to stray away from sportsmanship either. On our field yelling grenade and throwing a dummy wouldn't be a big deal. We do have some rules that make people shake their heads though; wether due to experiences or keeping important game dynamics. I'd say dummy grenades should be fine as long as no one is throwing anything dangerous.
One caveat, it could depend on where and whom your playing with.