We like Hewlett-Packard's HP Solve feature, which lets you solve for any variable without having to rewrite your equation. And, like most scientific calculators, the HP32SII can perform decimal/hour/minute/second conversions, polar/rectangular/angle conversions, unit conversions, base conversions, and arithmetic.
The LCD can display one line with 12 characters and is bright enough for most environments. The calculator runs on three LR44 batteries, which come with the unit.