Light TENT for light mountaineering use.

Maybe the Stephenson's Warmlight tent might be another good one to add to your list? The new Hilleberg "3 Season" tents also look nice and are probably more than suitable for light mountaineering.

I don't think I'd want to use my Moment in a moderate winter storm…

Stephensons Warmlite Climbers Tent? Sub-3 pounds for a (very tight) 2 person tent, but plenty big enough for one person.

Something like…a "traditional tent". (It's a joke.)

Go RAB with event.

Reportedly the North Face "Assault" tent is only 3lb without the vestibule.

Terra Nova Voyager superlight 3lb 7oz.

Hillberg Unna.

That new tent from Sea to Summit maybe?

There is a new Mountain Hardwear tent for 2012 – similar to the BD firstlight that will be 2lbs, 8oz. Freestanding.

I was going to suggest the Rocket, but it seems to be unavailable at the moment….

Single Person

MSR Hubba – 3lb 4oz (packaged, which means it can probably be trimmed to 3 or sub 3lb)
MSR Carbon Reflex – 2lb 9oz

Two person:
North Face Sputnik – 3lb 9oz (single wall)

Consider a Scarp 1 with crossing poles. I think it's around 3lbs, 12 oz.

Scarp 1 is not freestanding and to make it such would require 12oz poles (optional). It being not freestanding may reduce the number of campsites suitable for it.

So it is heavier, $100 more expensive than MSR Hubba ( which can be had for $199 right now)
http://www.usoutdoor.com/outlet/msr-hubba-tent1.html

$185 with shipping
http://shop.alpharettaoutfitters.com/products/MSR-Hubba-1-Tent.html

$199 free shipping
http://www.everestgear.com/msrhubbatent.html?productid=msrhubbatent&channelid=FROOG

The Hubba isn't much of a mountaineering tent. I have seen a pole break on one in 25mph winds and 3" of snow below treeline.