The best penalty take we have IMO is Joe Hart. This is completely ridiculous considering the ability to strike a dead ball some of our players have, but this is my reason.
As a keeper Joe Hart understands that there are places in the goal that he cannot reach when facing a penalty, when I've seen him he has put the ball near the top corner. Which is un-savable.
To be honest, I think it's a complete disgrace that top class players miss penalties so often. Tevez can hit the top corner from 30 yards, how can he not do it from 12 yards! You don't even need to go right in the top corner, just above comfortable saving height, and not down the middle.
Take this for example, this is possibly the best modern penalty save I've seen. And still, he gets lucky with his hand up, with that penalty Di Natale scores 9 out 10. Put it 6 inches higher or 6 inches further towards the post and he scores every time.
<a class="postlink" href="http://www.youtube.com/watch?v=QU0s1bHumIg" onclick="window.open(this.href);return false;">http://www.youtube.com/watch?v=QU0s1bHumIg</a>
Before anyone says keepers can dive to the top corner, first try it from standing, it's very difficult, and you have to completely commit to that one area of the goal and get your timing perfect, now imagine the ball is hit hard, you just aren't getting there unless you know where he's going to put it. Whereas dive to the foot of the post, it's easy, guess the right way and you save it, simple.
Rant over