I wear a 661 Pro Bravo Carbon, but honestly, I could really care less about how much it weighs. All helmets are probably going to be within a couple of ounces of each other. I wear mine when I know I'm gonna scare myself… otherwise I prefer to simply wear a Giro Havoc XC style helmet. To answer your question regarding weights however, MBA just reviewed a few popular helmets and here's their weight measurements:
Fox Rampage: 2 lbs, 7 oz.
Giro Remedy Carbon: 2 lbs, 4 oz.
661 Pro Bravo Carbon: 2 lbs, 5 oz.
Specialized Deviant Carbon: 2 lbs, 3 oz.
The One Carbon Fiber: 2 lbs, 6 oz.
Troy Lee Designs D2 Carbon: 2 lbs, 3 oz.
Primary rig: Devinci Ollie
AM rig: Norco Fluid LT2
Brodie Miscreant
'08 Buell XB12Ss Lightning
Thanks for letting me know what poo feels like.