Virtua Tennis 3

Go into exhibition mode and select Andy Roddick as your player. Then just hit a MAX serve once and it should be over 209kmh/130mph

If it isn't stand nearer centre of the court and aim down the middle, this usually gets faster serves than putting it out wide.

I found it best to plug in a second controller with a dummy account and go to the first mini-game under Court Games (Pin Crush). Then select Roddick for your account and whoever you want for the dummy account and just play the game.

You start with your account and try to knock down the pins, which is irrelevant here - the important thing is that every time you hit the ball it will be a serve hit, so you'll just have to focus on maxing it out just once. You'll get one/two tries each turn, then you'll have to do the same with your dummy, and then go back to yours until you get it.

I say it's fastest this way because every time you play you serve in this mini-game, and if you don't aim, most of the times you'll get two serves during your turn.

I unlocked it in my second turn, so it effectively took me 4 tries with my account + 2 with the dummy, less than 5 minutes. I think it might get longer than that if you're playing a match and you need more than 4 tries (assuming your opponent doesn't hit back any balls)