Most of the big online stock brokers give you access to a huge variety of stocks. Depending on how you trade, this could be cheaper than any other broker on this list aside from Robinhood. Schwab is also noteworthy for its various trading platforms. The Life Sciences sector includes companies involved in biopharmaceuticals, medical manufacturing and distribution, and bio products. Before you can begin trading in the penny stock markets, you have to call in and talk with a Fidelity representative about the risks. Cherney Reporter. Max A.