The Rayleigh collapse problem is defined as the collapse of a cavity in a liquid at a higher ambient pressure and is an idealized situation relevant in many applications related to inertia-driven collapse processes. In the simplest model the bubble is assumed to remain spherical during the entire collapse process leading to an extreme concentration of the energy of the system. The solution of the bubble radius evolution for the particular case of an empty void has a singularity at a finite time that provides the well-know Rayleigh collapse time. In this talk we will revisit the analytical expressions for the singular collapse of gas/vapor bubbles to show that, for sufficiently intense collapses, this singular solution can be used to predict amount of viscous dissipation and acoustic energy emitted as well as to capture the influence of the presence of deformation and non-condensable gases on the peak pressures and temperatures that can be reached. In addition, for non-spherical bubbles initially in contact with a wall, we will put in evidence the presence of an additional singularity in the initial acceleration field that will be shown to clearly distinguish two different regimes of bubble-wall interactions controlled by the contact angle. Comparisons with experiments carried out at EPFL [Preso et al, 2024] and ENSTA Bretagne [Saini et al, JFM, 2022] will support the conclusions from the theoretical and numerical studies.