The retro style 12c financial calculator was the first to use the landscape layout and tiny replaceable batteries to let the device fit in a shirt pocket. Though it's currently available as a mobile app, the 15c scientific calculator is also making a comeback. The vintage look remains, but with a processing speed 100 times faster than the old version. The financial calculator is available for $80 and the scientific is $100. Sure, you can use the calculator on your phone or computer for graphing homework and finances, but those are so boringly modern.