Check out these videos, showing the "knuckleball" technique. As you may already know, simply, this is the technique players such as Cristiano Ronaldo have used over the last few years - confusing more than a few goalkeepers, and scoring many goals, due to them having the ability to control the ball in mid-flight.
I'm only a few days of away of owning the final retail copy, so I've been forced to try this out on the demo. So far, it seems quite hard to pull off - which is a good thing for me. If it was easy, then I feel this particular feature would get abused or over-used (but it may just be me, not being able to perform it correctly).
Anyway, I admit that I haven't been aware of this technique for long and I was pleased when I saw that it being included in the final game.
I'm not sure if the majority of the PES community know about the knuckleball so be sure to spread the word, guys!