The TI-36X Pro is one of my all-time favorite calculators. Some great features of this calculator are that it can
Solve two-step equations, like 3x-3 = 12
Solve polynomial equations, like 2x^2+4x-12=0
Solve systems of linear equations in 2 and 3 dimensions
One-button switch between fraction/decimal, pi/decimal, and square root/decimal answers
Logarithms with a base other than e or 10
Derivatives
If you like this calculator, you may also enjoy other calculators from Texas Instruments. I have also used the TI-30XIIS Scientific Calculator and the TI-84 Plus Graphics Calculator.