Essentially, ANY revolver with a hammer mounted firing pin will fire if the weapon is dropped on the hammer with the hammer down on a loaded round This includes basically every revolver made until the invention of the frame mounted firing pin, and then MANY models even thereafter that did not make concessions to STOP or DISCONNECT the frame mounted firing pin until the trigger is pulled. Specific models would include the Colt Single Action Army (or any of its clones), or the Smith & Wesson Model 10 (aka S&W Military & Police) & Model 13, Model 29 or 629 (Dirty Harry), early Colt Troopers in .38spcl, etc etc.
Any number of hammered pistols and revolvers without specific safeties like pin block safeties (like Glock) or two piece firing pins (Marlin), or "transfer bar systems" (like the Ruger design, as well as Taurus) . For example, a 1911 or a Browning Hi-Power pistol with the hammer down on a loaded chamber (safety would be off by design) would fire if dropped on the hammer. The Heritage Rough Rider .22lr revolver has a frame mounted firing pin (not hammer mounted), but it does not have any internal pin stop features, so it WILL fire if the hammer is struck when the hammer is down on an empty chamber.
And then there are those flukes, where a striker fired weapon that doesn't have sufficient sear pressure and no firing pin block safety can "slip" if dropped.
Alternatively, there are modifications that if improperly pursued can also cause a weapon to discharge when dropped. I've known a few shooters with Ruger Mark II pistols (internal hammer fired) that "polished the sear" to improve their trigger pulls, but ultimately made the weapons unsafe by removing too much sear pressure, allowing the sear to "slip" if the gun is dropped.