I am currently using Myprotein Impact whey at 1.5g carbs per serving. It's about £17 for a 1kg bag and there are lots of flavours. I have used lots of shakes previously (Atkins Advantage, Sci-MX Diet, Herbalife Formula 1), but the one I am using now seems to be be the best value for money, and is the lowest in carbs (which you may not be looking for, but I am)