Generally, a supercharged V8 is the kind that you'll be most likely to have come across, although there have been numerous supercharged V6 models and even supercharged inline engines. The reason for this is the wealth of low-end torque produced by a V8, which helps offset the power sap that a supercharger causes at very low rpm. V8s also displace a lot of air, and the more air there is to compress, the more impressive the effects of the supercharger will be - assuming that the supercharger is right for the application, of course.