I'm surprised (and a little disappointed) that nobody has posted here about Paddle Force yet.
It's a "remix" of the classic Pong that actually changes the game's rules in a significant way. Knocking the ball into the back of the opponent's court doesn't just give you a point-- it expands the size of your court and shrinks theirs. Your paddles can move freely, but only in their own area. Your paddles can also twist clockwise and counter-clockwise, and if you time your twist right, you'll get an extra hard hit towards the opponent. There are also a few power-ups that make the game more interesting without getting in the way. If you want the game to be a little less chaotic, you can turn off power-ups as in the Smash Bros. games.
So please, check it out. And if you dig it, kick the developer a few bucks. This one is worth it.