In this tutorial review, we provide an overview of the recent research toward surface functionalization of plasmonic nanoparticles for the generation of advanced optical sensors that make possible the analysis of various moieties by means of surface enhanced Raman scattering (SERS). Such moieties include atomic ions, low affinity target molecules, inorganic anions, biometabolites, pathogen markers and/or other analytes of interest even under very demanding circumstances such as those related to real life samples. We expect this review to be of interest to researchers in a broad diversity of fields that can take advantage of the unprecedented sensitivity of this type of molecular spectroscopy, in a wide variety of analytical and bioanalytical problems.