In this discussion, "will" is basically synonymous with "the ability to make choices." Free will means that our choices (and the choices of others) can have consequences.
It is in the context of choices that we can begin to dissect the meaning of will.
As with so many other "human" topics, I find Peter to be the most helpful, as he's seen in contrast to Jesus.
Thus, in the Garden we see Jesus faced with a choice: between what God wants, and what Jesus (as a human) would rather do. The price of choosing to do what God wants is enormous; the choice to avoid immediate suffering and death is both low and immensely attractive.
We see Peter faced with much the same choice -- though his choice (merely to admit that he knows Jesus) is apparently much easier. And yet Jesus chose well, and Peter did not.
In both cases we see acts of will. In this story, not to mention most of Jesus' parables, the whole point is what we do with our ability to make choices. It's not that we have always to make the right choice -- it's that we try to do so, and are properly sorry when we don't.
(Of course, the reason we all identify so well with Peter, and gain hope from his example, is because God does not abandon Peter when he makes the wrong choice, but instead strengthens him to make the proper choices when he faces them again.)
I suppose it's also appropriate to look at the role of Judas in this story, his choices, and the consequences of his actions, but I guess that would probably take us pretty far afield.
If the label mystic fits me or the label dualist then be my guest!