What is the best supplement for mass building?

i think mass protein gainers really help but the main thing is not supplementing them FOR food but adding it to your normal caloric intake..

ones i've taken/enjoyed:

MONSTER MASS
MASS XXX

mass xxx more-so cuz of less fat, but when working out hard i like monster mass post w/o and mass xxx maybe as meal replacement "between meals"

best mass/weight gainer out there is probably ISO-Mass Extreme Gainer by Ultimate Nutrition, not the best tasting by any means but it has everything you could want and for roughly $40-$60 you get 90scoops/30 servings

If your lookin for lean mass the best protein ive found is Pro Complex 60 grams of protein and its very lean. If you want a weight gainer i like cytogainer or mass xxx from gnc.

To combine a long term massbuilder, i think a combination of this is the ultimate:
1.before workout:Creatine and carbodrink to fill up the cells with energy to perform a great workout.
2.After workout:Recovery drink containing glutamine,creatine and some carbohydrate.
3.After workout 2: 45-1 hour after workout Proteindrink with an amount of 25-40g of high quality protein(whey to prefer to its fast acting profile)This is taken with your meal.

The creatine drink before workout should be taken for 4-5weeks for best result.
After that period just take carbodrink. Then repeat the cycle again. Dont forget the rest between workouts.
None of these products are that much expensive, and is all your body needs for natural gains in both mass and strenght(my opinion).