To everyone:
Thanks for all the helpful suggestions. Obviously, we weathered the weekend without any events. But, you never know...so, to clarify my original question, here's the sceneario I was envisioning - (which is similar to what most people faced during 9/11):
You find out there's an attack somewhere in the city nearby - say within five blocks. It could be chemical or bio, but most likely is just a garden variety hit on a fixed location, like a building. That could mean an explosion, another airplane, or something new. You are given an order to evacuate immediatley because know one knows what will happen next. People are hysterical and heading for the stairs. Security guards and/or policemen may be keeping you from returning to your office, cubicle, cloakroom or anywhere else you might have stashed gear. So, you must get out, NOW.
This likely means that your whole kit must be carried in the pockets you have on you (or at most in a very small back/fanny pack). For most NYC dwellers, that it be only a minimum of multi-use gear that can be carried at all times during office work and back home again without attracting undue attention. So, door breachers, complete changes in clothing, illegal knives and unlicensed guns, while certainly useful in some situations, are probably out. Remember, when you left the house this morning, there was no attack so all the usual rules applied while gearing up. And, you're going to have to walk home, so getting pegged (falsely) as a terrorist by a jumpy cop who sees what he thinks to be unusual weaponry isn't going to help you in any way.
So, given all that, what would you take with you and how would you take it?
For me, it's come down to cash, whistle, keys, bandana, multi-tool, flashlight, compass, map, and cell phone. If I happen to be by my desk, I get the added benefit of a fire escape hood, water, my palm pilot, folding knife, first aid kit, some food bars, rope, tape and walkman.