Multiwfn

Multiwfn is a command line program that enables you to perform general wavefunction analysis, including topology analysis. The app can be run as standalone via PowerShell or Command Line, but you can also embed it into shell scripts.
Considering the functions included as well as the fact that it is specifically designed for realizing electronic wavefunction analysis, it can be a key program to use for anyone using quantum chemistry. Some examples of the functions you can perform via the app, you can include displaying the molecular structure and orbitals, calculating real space in a plane and plot plane map, AIM analysis, gradient paths, drawing interbasin surfaces or population analysis.
Speaking of real space functions, this is one of the strong points of the app according to the developer. Counting more than one hundred functions, you can gain valuable insight about electron density, electron spin density, electrostatic potential, average local ionization energy, single exponential decay detector (SEDD) or the magnitude of electric field.
As you probably figured it out by now, the program can come in handy for a wide variety of research that involves characterizing chemical bonds, electron distribution and variation, aromaticity and electron delocalization analysis as well as intramolecular and intermolecular weak interactions.