A free graphing calculator. An abridged algebra system. Or a glorified tip calculator.
Nowadays our phones have high-res screens, Wi-Fi, 4G, and all of the GBs. So why use a physical graphing calculator from the 1980s?
-2D/3D graphing
-Scientific calculator
-Fractions and complex numbers
Basic computer algebra system:
-2D tracing and root finder
-Inline sto() function
-Function tables
-Numerical derivative/integral
-Probability distribution functions
Full version with more features also available.
NOTE:
-sto() function may be used for infinite series/mathematical induction, Newton's Method, etc.