The Hewlett Packard HP-48G

Display: 4 line LCD, plus status & menus, 131x64 graphics

Power: 3 AAA cells

Adv. Functions: You name it, it's probably got it, from a solver to symbolic calculus to built in equations for fluid dynamics to an RS-232 serial port to up/download programs and data.

Memories: limited only by RAM

Programming: 32Kb user RAM, RPL language.

Comments: This is actually the low end of the 48 series. The 48G+ has 4x the memory and the 48GX takes expansion cards.