The HP-32S still holds a soft spot in my heart, even though it only had 4 registers. I have fond memories of writing a nonlinear solver for finding an azeotrope curve during a Thermodynamics final. Despite the increase in power, memory, pixels and features the HP-32G that followed never could steal my heart away. Here's to you, HP-32S.

Let's hear it, what's your favorite programmable calculator?

As with all poll type questions, do NOT submit a new answer unless your answer is not represented. Vote up your answer instead of adding yet another TI-85 or HP-49 to the list, and add comments to that answer if you want to relate specifics.

EDIT: I moved my photo into an answer for polling.