As transient surveys become wider and faster, and followup facilities become more automated and global, we are able to discover and characterize new phase spaces of transients. Among these I will review new classes of supernovae which evolve either too rapidly or too slowly, or emit too much energy to be explained by conventional models. Even as more events are found in each of these classes, their progenitors and the physical mechanisms driving them, remain a mystery. I will also mention new and diverse classes of transients which we are discovering in galaxy centers and believe are tied to accretion onto supermassive black holes. Hopefully, new observations and theoretical models will continue to help uncover the mysteries of extreme transients, and what physics and astrophysics they can teach us.