We will explain why near-extremal black holes can be used as probes of new physics. Our journey starts by exploring near-extremal black holes with anti-de Sitter boundary conditions in Einstein-Maxwell theory. We show that, in almost all cases, tidal forces diverge as one crosses the horizon, and this singularity is stronger for larger black holes. In particular, this applies to generic nonspherical black holes, such as those satisfying inhomogeneous boundary conditions. Nevertheless, all scalar curvature invariants remain finite. Moreover, we show that nonextremal black holes have tidal forces that diverge in the extremal limit. Next, we will discuss how the same mechanism generates large tidal forces for near-extremal black holes with asymptotically flat boundary conditions due to the presence of generic higher-curvature terms in the gravitational action generated by quantum corrections to general relativity.