Taunt opponent
Press Left Analog-stick Up, Left Analog-stick Down, Left Analog-stick Left, Left Analog-stick Right, Black, or White.
Recommended Tennis Racket
It appears that the tennis racket you can purchase for 5,000 coins has different effects depending on how much power and accuracy you have on your swing. Although there are no stats regarding the tennis rackets you can purchase (abilities, strengths/weaknesses) the tennis racket that you start with is by far the best racket you can use.