I say zero.
Now you've got me wondering if Canadians and others outside the US always call a "z" a "zed" or a "zee"? I've been under the impression that Canadians always said "zed".
We say "zee" you see.
Zee, what the hell is "zed"?
What do you people say for decimals, eg "0.5"?
I just drop the zero and say point five, or in that case turn it into a fraction, one half.