In Macbeth, how is the theme of sacrafice displayed?

I think one instance that clearly displays the theme of
sacrifice is in Act III scene 3, where Banquo is shown to sacrifice himself so that his
son may go free and carry on Banquo's line in spite of Macbeth's attempts to secure his
throne against the prophecies of the witches. As the Murderers surround Banquo and
Fleance, note how Banquo responds and what he says:

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O, treachery! Fly, good Fleance, fly, fly,
fly!

Thou may'st revenge--O
slave!

The majority of
productions show Banquo tackling the Murderers himself whilst he utters these final
lines before he dies, so that Fleance has an escape route away to safety. This of course
shows us a lot about Banquo's character in comparison with Macbeth's character.
Throughout the play, Banquo is used as a foil to exaggerate Macbeth's evil, and here we
see Banquo's goodness and self-sacrificial nature in his willingness to die himself so
that his son may live.