Oceanic Delta4 FDX10. I have dove the reg for two years now and have had it down to 37*F @100ft and have felt no reduction in breathing effort. Adjustable 2nd stage with venturi switch is very nice. It also automatically adjusts for set breathing efforts as you descend or ascend. Also, it has a swivel head which makes it more comfortable(although may be viewed as a failure point I have heard of or had no problems), is nitrox compatible to 40% out of the box, and has Oceanic's Dry Valve Technology that helps protect internal components. Cost is about $525 at LDS, but can be found cheaper online.
Also, this is an article I found on the board on some ago. I forget who originally posted it so I can not give them credit (sorry for that!):
The National Oceanic and Atmospheric Administration announced its new regulator pick. In the June issue of Undercurrent, we wrote about NOAA's new rules and regulations for government divers in response to the death of two Coast Guard divers in Alaska last summer. One major change was giving the boot to all regulators Coast Guard divers had previously used for cold-water diving. After testing of multiple regulators, NOAA found Oceanic's Delta IV to be the most reliable.
"It consistently came up first for meeting all our criteria, and it won't freeze up in cold water," says Lieutenant Eric Johnson of the NOAA Diving Program. The Delta IV is an environmentally sealed diaphragm regulator and its first stage has Oceanic's Dry Valve Technology, designed to stop moisture and contaminants from entering and to prevent corrosion of internal components. NOAA bought 350 of the regulators and now requires its 500 divers to use that model when diving in water temperatures of 50 degrees or less. Johnson says the Navy's experimental dive unit is using them, too. The Delta IV is also commercially available for sport divers; Oceanic's suggested price is $570.
Cold-water divers should definitely invest in a good regulator that won't freeze up underwater. Two people died last April because of that problem. Jason Balsbough and Daniel Frendenberg, both age 21, and Sherry Eads, 43, went diving in a quarry in Gilboa, Ohio, where the water temperature was 38 degrees. Another diver called 911 to report the divers were down. Balsbough had regulator problems but was able to surface by himself. Frendenberg and Eads were too deep and their regulators were too iced for them to breathe.
