Nearly
all bodybuilding supplements are "worthless", so much so that it seems ridiculous to have an entire forum dedicated to them.
Protein powder can be useful as a convenience, but it's really no different than what you're getting from meat and eggs.
Creatine is effective for some people in getting an extra rep or two out of your sets, but the difference in your overall results is marginal at best.
Vitamins/minerals are always a good idea for overall health, but they won't improve your bodybuilding results.
Anything else, don't waste your money. Ephedra was very effective for fat loss, but of course you can't buy it anymore. No matter what anyone says, BCAA's and Glutamine are just protein, and if you're getting enough protein overall you're already getting these amino acids. "Growth hormone releasers" are a joke... if you want GH, buy the real stuff and inject it. Tribulus and other things purported to increase test levels are also a joke.. if you want test, buy it and inject it. Some of the other whacko things out there like "myostatin blockers", "isoflavones", and etc are pure snake oil.
There are supplements like fish oil, Co-q10, ala, etc that have useful applications for health, but again are worthless for bodybuilding.
GNC should just close its doors and save everyone a lot of trouble.