It charges via USB, is waterproof, and has eight settings. It's also got a feature called "cruise control," which means it saves the last 20% of its power until it senses that you're pressing it hard against you, so the motor will automatically stay as powerful even ~under pressure~. Yeah, it's basically magic. Check out BuzzFeed's full write-up on the Sona.
Promising review: "I'm usually big on super powerful, wand-type vibes that are like jackhammers, as I prefer pressure and deep rumbly vibrations on a large area versus precise clitoral stimulation. The Sona Cruise is definitely precise stimulation, but it's different. Really different. It took me a few tries to find THE SPOT to place it, and it's really weird at times to just let it sit there and do its thing instead of pressing it hard against me like I would with a wand-type vibe, but the orgasms from this thing are UNBELIEVABLE. I'm glad I went with the Cruise model versus the regular Sona, as it has an extra burst of power when I do press it up against me harder, and that helps push me over the edge. I also appreciate that it's small and easier to transport than a larger vibe. This comes with a pouch and could be thrown in my purse and no one would be the wiser." —Wildflower345
Get it from Amazon for $86.99+ (available in three colors). You can also get a less expensive version without the "cruise control" feature here.