What's the closest to a "Hollywood style" chemical weapon?

Factual Questions
1

Chemical weapons, as depicted by Hollywood, are kind of funny. At least in their characteristics. Y’see, your typical poison gas in the movies…

•Takes the form of visible clouds of vapor.
•Is deadly to inhale only, and
-Can be completely protected against with only a gas mask, not a full protective suit,
-Is non-persistant, not contaminating surfaces or terrain, and dissipates quickly,
•Kills quickly, like within a minute.

The thing is, though, from all I’ve casually studied on chemical warfare, I can’t think of any actual agent that fits all of those criteria. I actually think something like Halon or Nitrogen asphyxiation might be a closer fit, disregarding the “ominous yellow-green smoke” requirement.

It’s gruesome, to be sure, but…can anyone more in-the-know think of any chemical that fits the Hollywood style deadly gas better?

(And no, for the record, I don’t want to make any, buy any, use any, or advocate the use of any on anyone or anything, thank you.)

2

Other than the visible cloud, HCN is pretty close.

3

Depending on how strict you are with some of your rules…Maybe Pepper Spray. It doesn’t typically kill but all you really need to protect yourself from it is a gas mask. However the residue, from what I understand, will stick around, but it’s not going to hurt you so long as you don’t get it in your eyes/nose/mouth. Also, even if you use it with a gas mask, I would assume you’d want to take a shower afterwards. I’ve heard of people finally recovering from getting sprayed only to have some sweat (or water from a shower) run down their forehead hours later and it starts all over.

Maybe this really isn’t quite what you’re looking for.

There may be a nerve gas that would fit the bill though.

4

Sounds a lot like weaponized chlorine gas used in WWI.