Smallest bike I've had since I passed my test was the CX500.
Although I love larger capacity sports bikes, I quite like 500’s I owned a GPZ500 for a couple of years, It was just a spare hack that I used whilst other bikes were in bits. I also owned a 1973 Yamaha TX500, the worlds most fragile bike, although mine seemed to keep going (as long as you kept the speed under 60 mph!)