The top-selling cell phone accessory on Amazon, the Jackery Giant+ portable USB charger, is discounted to $29.99 ($10 off) today. If you ever need to charge your phone or tablet without access to a wall outlet, this 12,000 mAh external battery will do the job for you. Chargers like these are essential for travelers, people with long workdays, or those who just don't like getting off the couch to plug things in.
Note that only the orange color is discounted today, so you'll have to pay a little more for the eye-catching gold color or the neutral silver and black versions.
The Giant+ supports 5V/2.1A output, which charges phones and tablets more quickly than cheaper chargers. It can also charge two devices at once, though one of them will charge more slowly with 5V/1A output. This external battery has enough juice to charge most tablets at least two times and around four full charges for typical phones. Of course, all you need to do once the Giant+ itself is out of power is charge it with a conventional wall charger.