Which programs do you actually use in your calculator?

[Vtile]

HP50g:

PEQUM Equation Library Manager (I wish there were a source code somewhere)
Equation Solver
solve -command (usually just manipulating some basic engineering functions for ie. sanity checks)
default program editor
->tag -command
Unit conversions
TMENU with custom set of most frequently used units.
Graphing functionality to check odd curves of ie. resistor networks
I would use binary manipulation programs if there would be a good set of those (WIP some Quick and Dirty ones for personal needs)

Why? Because I do not have access to math tools (except windows calc) at work PC ...and 'they' claim that calculators are useless at this decade. Nonsense.