Get Smart was terrific, though I felt its humor relied too much on repeated catchphrases. It was a fun pastiche of the '60s spy craze, though a lot of its humor is probably lost if you're not familiar with the things it parodied.
Just in general, the '60s were my favorite era for sitcoms. There were so many imaginative, formula-breaking shows. It wasn't just family sitcoms and school sitcoms and workplace sitcoms. You had Get Smart, a spy show; Gilligan's Island, a survival narrative on a desert island; superhero shows like Batman and Captain Nice; science fiction premises like My Favorite Martian and My Living Doll and It's About Time; fantasy premises like Bewitched and I Dream of Jeannie; fourth-wall-breaking, surreal stuff like The Monkees and Green Acres to an extent... it wasn't always brilliant, but it was rarely boring.