Sidney Poitier's crowning moment of awesome in indisputably when a rich white bigot slapped Poitier's character, Det. Virgil Tibbs, for daring to question him on suspicion of murder. To the shock of white viewers and the delight of black ones, Tibbs instantly slaps the bigot back, an act that was previously unthinkable for African American characters in mainstream Hollywood films.
It gets better: the original script had Tibbs simply accepting the slap, with the idea supposedly being that he was showing himself to be the bigger man. Poitier himself insisted that audiences wouldn't see it that way, and he had to slap the guy back.
"They call me Mr. Tibbs!"
Gillespie gets one when he rescues Tibbs from an angry mob of racists, authoritatively, by slapping one and gut-punching another - left-handed. Despite him wanting Virgil to leave in the first place.
Tibbs talked his way out of getting shot/killed by a second angry mob by getting the mob leader to realize his sister was at an abortionist's with the man who really got her pregnant.