I tried today the Aqua Lung Technisub Micromask, $79 from FreediveStore.com Aqualung Technisub Micromask. This Aqualung micromask really lives up to its name. You want to talk about low internal volume, it has no internal volume. Seriously, the omer abyss is a low volume mask, I poured as much water into it as it will hold without spilling and then I poured the water from the omer abyss into the Techinsub. the water kept spilling and spilling out of the Technisub Micro mask. It was almost like the only place that held water was the nose pocket.
The Aqua lung Technisub Micromask is constructed differently than any mask I've seen. The plastic frame is bonded/merged with the skirt. Field of view is very good. The buckles swivel in four directions. The mask is comfortable and light. As small as it is I think it's amazing that the frame doesn't put any pressure on the bridge of the nose. I think it's a great low volume spearfishing & freediving mask.
EDIT 5/8/2012 - A similar mask, the Speardiver Micromask is now available for for $49 Speardiver Micromask.