I'm all about Muscle Milk. Actually helped me get where I wanted to be really quick. By working out, having a decent diet, which I still ate pizza and burgers, I lost 47 lbs and packed on 14 lbs of muscle in a short period of time, about 3 months I believe. Not trying to be a poster boy for it but it worked for me. If I didn't injure my back and not been able to workout i'd be in the best shape of my life right now. Now I'm getting back into it and believe me, Muscle Milk is my only choice. Not for everyone though, I know some who it didn't work for. Mass gainer, I love Muscle Tech products. My stack was Muscle Milk 3 times daily, once before workout and after, and before bed. Then I took Cell Tech, basically creatine, i think that was the name, and NO boost, can't remember the name.
I know they aren't really mass gainers, but a good one is Cell Mass.