Honestly, Northern Lights is the strain that I though of first when I saw your question. NL is 100% stable, meaning that you won't get any crazy phenotypes (different looking plants in Laymen's terms, for you non science folk, lol) from your batch of seeds. It has also been used to make some of the most popular/potent strains that have come out in the last 10 years. Stinky has posted some excellent strains as well (Skunk #1 is amazing if smell isn't an issue). I really don't think you can go wrong with any of the strains posted.