The question Is there an alternative to SIMION? was posted recently on the physics site. It sounds like something that may be better suited for this community, but I'm not sure to what extent software-recommendation questions (or other threads that can be argued to fall under the broader 'shopping' umbrella as defined in the early days of SO) are welcome or encouraged here; I looked on this meta but I couldn't find anything explicit, either because there isn't an existing thread with the right keywords or because I just mucked up the search.
Are questions like that one on-topic here?