From what I've read, a lot of people (myself included) are using cold tap water. I've seen guys go to the extreme and throw ice cubes in their sink and whatnot, but I reckon that's a minority of folks, especially in winter seasons.
LOL. I used to use just cold tap water... when I lived in Colorado. Now I'm in South Florida and the "cold" tap water is warm enough to shower in, so it's the ice cubes in the sink.
I've been cold shaving for a while and I think the idea is that you just want the water cold enough to get your skin to contract - I'm guessing 50 - 60 degrees.