None of my cats are extremely graceful, so it definitely doesn't enhance their speed and performance.
Vash's tail is his own personal toy.
Spaz's tail is a fashion accessory and a morse code transmitter.
Shadow and Trouble's tails are bait.
Cassi's tail is a toy for others and a morse code transmitter.
Ivory only started doing stuff with her tail recently, it's a fashion accessory, and toy for others and bait. Until this year though, it only ever hung straight down, we actually thought it might have nerve damage.