PowerAll Rosso Red/Black Portable Power Bank and Car Jump Starter for only $79.77 + Free Shipping, 33% off the list price of $120. This is the #1 selling item in Amazon's Automotive category, snagging a 4.5/5 star reviews.

On a full charge this power bank can jump start your car 20 times. (Let's hope you never have to test that number.) It's a great addition to the trunk.