One full failure in an SEP, it was an ancient arrow 1 and it stopped just before the flare so no real dramas. Although I've also had one stop due to running a tank dry.....whoops but switch tanks and all was well.
Several rough runnings due to fouled plugs, dodgy mixture controls, overheating etc.
And one failure in a fully loaded twin that decided to spit all of its oil all over the shop. Although I've shut down more than a handful more engines on a twin while teaching the MEP course, but that doesn't really count as it was fully intentional.