Casio FX-CG50 Graphing Scientific Calculator for sale online | eBay
Casio fx-CG50 の概要 - e-Gadget - プログラム関数電卓
Update: It really does go without saying, the FX-CG50 is a beast of a calculator. But my trusty FX-991EX is still good for a lot of things. They are both good calculators. :