Any pure protein supplement made by a good company is acceptable. Read articles, research this site, and evaluate yourself to find out what your protein needs are and how much you can afford to spend on em.
Biotest's Low-Carb Grow! and Optimum's 100% whey are my two favourites. Not just because they contain some of the best stuff around at any price, but also because they are companies i can trust and label claims have over and over proven to be effective, also both products are very cost effective.