Nitric acid molecule: The figure is a result of Kimball's heuristic "spherical cloud" model. It takes about 10 sec to optimize geometry and obtain the energy minimum by Silvan Perego's program KIMBALL (diploma thesis, University of Bern, April 1989). The input is trivially simple. Just choose "EDIT/add nodes" from a graphical table, add H-atoms automatically, click "CALCULATE/optimize" and there it goes. You can watch the optimization of the clouds while the energy minimum is searched. This comes out to be -279.3841 as compared to ab initio programs in the table:
 
Program Method/Basisset Total Energy (hartree) Virialratio -V/T
Kimball (standard params.) Spherical "Clouds", homogen.     -279.3841   2.00006
Gaussian94W UHF/6-31+G(d)     -279.45369679   2.0028
Gamess-PC UHF/6-31G (NDFUNC=1,DFFSP=.T.)     -279.453696801   2.0028
Gamess-PC as above, but with virial scaling     -279.45467049   2.0000001

Below stereo plot of the final Kimball structure. The "p" clouds are in cyan, above and below the s-skeleton. All the methods find the same point group and very similar geometries (compare  F2CO ).