Barriss Offee had the ability to use floating meditation, which looks kind of cool. She's also a skilled Jedi healer with very strong telekinesis abilities. She and her master held up an entire cave roof that was collapsing long enough for Yoda to arrive to rescue them. The Jedi-pedia says that Offee can force choke someone to death without even being in the same room or being able to see them. Even Vader couldn't do that.
I was really surprised that Barriss Offee turned to the dark side in the last episode of the series. And I'll probably always want to know what Luminara Unduli would have to say about that. Below is the speech that Barriss gave to the Jedi Order shortly before she was sentenced for the terrorist attack on the Jedi Temple.