My 2 cents:
PAST is used in different research fields and is tailored particularly for palaeontology. Lots of modules; very good graph facilities. Used by scientists world-wide. Worth keeping on your computer.
JAMOVI: an free and open source alternative to the more cumbersome SPSS. Modules can be added to expand its functionalities; not so many currently available. Output tables in APA style (which can prove handy); charts and plots' quality depends on the module used. It builds (under the hood) on R, which is good. I like the integration with R (which can be executed from within Jamovi). I use JAMOVI for two study units I am currently lecturing. Not bad. I hope that the list of modules will grow in the near future. Can be used as a "bridge" to R.
I would add
Orange: lot of modules here as well, including text mining. I like the fact that the analytical steps are build via widgets. Can be handy and fun for teaching. I do not really like the way data have to be fed into the program. For the rest, I think it is another software worth installing.
R of course (otherwise
@Dason will start complaining): steep learning curve, but its functionalities and potential are unbounded.
Best
Gm
EDIT
JMP I really like this; its concept is different from other software as it rests on the idea of data exploration. Lots of graphical and analytical options are "hidden" into sub-menus; this allows to digg really deeper into data. I would suggest this to people who are already more than familiar with stats.