Hamlet's Tragic Flaw

One of the staples of theatrical tragedy is the idea of the 'tragic flaw'.  The protagonist (usually the title character) has some thing that wrong with him that ultimately leads to his downfall.  It has long been suggested that Hamlet's tragic flaw is his hesitancy.  He doesn't react quickly enough to the kill his uncle.  This gives Claudius enough time to plot Hamlet's death.
Hamlet's prime opportunity comes in Act 3, Scene 3.  Hamlet has seen the king react to the players, he is convinced of his guilt.  He comes upon Claudius praying.  The stage direction has Hamlet enter as he finishes (though obviously you could play this so Hamlet hears the whole confession).  Earlier Hamlet heard the ghost of his father complain that he was in hell because he had been taken unawares.  Now if he dispatches Claudius while he's in a state of grace then the villain will go to heaven. 
Hamlet:

Now might I do it pat, now he is praying;
And now I'll do't. And so he goes to heaven;
And so am I revenged. That would be scann'd:
A villain kills my father; and for that,
I, his sole son, do this same villain send
To heaven.

So in his speech he decides to wait a bit:

Up, sword; and know thou a more horrid hent:
When he is drunk asleep, or in his rage,
Or in the incestuous pleasure of his bed;
At game, a-swearing, or about some act
That has no relish of salvation in't;
Then trip him, that his heels may kick at heaven,
And that his soul may be as damn'd and black
As hell, whereto it goes.

That's the straight reading of course.  We don't have to take it at face value.  This could be Hamlet's way of avoiding a conflict.  That's one of the beauties of Shakespeare, there is plenty of room for interpretaion. 
What's interesting to me is that if you changed the title of the play to 'Claudius, King of Denmark' you would have the classic tragedy.  Just picture it, a man seeks the throne.  Maybe he just wants power.  Maybe he thinks that the king is unworthy.  Maybe it's a scheme born out of lust with Gertrude.  Who knows?  Anyway, he has taken the top spot through poison and in the end, by poison he dies. 
Classic.