In Act III, Scene I of Macbeth (and only scene I please), what are the literary devices used?I cannot find that many and I know that they are...

Concerning your question about Shakespeare's Macbeth, I'll just start at the beginning of the scene and list a few devices for you.

• Soliloquy--Banquo's opening speech


• Repetition--"As the Weird Women promised"


• Metaphor--"played'st"


• Metaphor--"stand"


• Metaphor--"root"


• Metaphor--"shine"


• Metaphor--"gap"


• Metaphor--"Forever knit"


• Metaphor--"take"


• Metaphor--"fill up"


• Metaphor--"borrower of the night"

You get the idea, and that's enough of metaphor.  Irony is also involved at the beginning of the scene.  When Macbeth tells Banquo not to miss the feast tonight, that is ironic because Macbeth knows Banquo will not be at the feast tonight, since he's going to have him killed.  The same irony occurs when Macbeth tells Banquo that the two of them will discuss Malcolm and Donaldbain on the next day. 

Finally, I'll "throw in" some personification.  When Macbeth says that Banquo's wisdom does "guide his valor" (Act 3.1.55) he is personifying valor, just as he personifies genius when he says "My genius is rebuked" (Act 3.1.58).