Which stylistic devices are used in Hamlet?

Allusion plays a significant role in the development of the play and its themes. There are many allusions to the Bible, including a few to the Garden of Eden. For example, Hamlet says,

O God, God,How weary, stale, flat, and unprofitableSeem to me all the uses of this world!Fie on 't, ah fie! 'Tis an unweeded gardenThat grows to seed. Things rank and gross in naturePossess it merely (1.2.136–141).

Hamlet compares the world, now that his father has died and his mother has married her brother-in-law (who is, by canon law, her own brother) so quickly, to a garden that has become overgrown and rotten with weeds. This seems as though it could be a reference to the Garden of Eden, after Adam and Eve committed the original sin and fell from God's grace. They were cast out of Paradise and not allowed to reenter. Hamlet's mother and father, likewise, seemed to occupy a Paradise in Hamlet's mind while his father lived, as they seemed so perfect for one another and so happy. Now, however, Paradise has become corrupted by his mother's sinfulness (just like Eve's), and everything Hamlet looks upon disgusts him.
Furthermore, Hamlet's father was poisoned in his own gardens. The ghost tells Hamlet,

Now, Hamlet, hear.'Tis given out that, sleeping in my orchard,A serpent stung me. So the whole ear of DenmarkIs by a forged process of my deathRankly abused. But know, thou noble youth,The serpent that did sting thy father's lifeNow wears his crown (1.5.41–47).

The ghost of Hamlet's father uses a metaphor to compare his brother to a serpent (the very creature into which the Devil changed himself to tempt Eve to sin in the Garden of Eden). Here, then, another allusion to the Garden of Eden paints Claudius as the Devil who corrupted Paradise, who morally ruined Eve/Gertrude. We see, through this allusion, that there is no redemption for this kind of moral ruin; all of the "rot" must be excised from the Danish court. Everyone involved in the rot must die, and Denmark must start over with a new ruling family.

One rhetorical device often used in Hamlet is metaphor. When Hamlet discusses how Claudius has damaged his kingdom, he says "Tis an unweeded garden that grows to seed." This is a metaphor because it is a description based on an implicit comparison between the kingdom and an untended garden.
Hamlet also contains similes, which are direct comparisons using the word "like" or "as." One example of this is "Reason, like sweet bells jangled." Shakespeare also frequently employs alliteration, or repetition of beginning sounds in words. Examples include the phrases "frighted with false fire?" and "Be soft a sinews."Lastly, Hamlet contains many allusions, which are indirect references to past works. For example, Claudius references Cain from the Bible when he says "It hath the primal eldest curse upon't, A brother's murder!"