ANTONIO: ..That most ingrateful boy there, by your side
From the rude sea's enraged and foamy mouth
Did redeem
The example above represents an allusion.
The allusion is a literary device that refers to a certain person, thing or event by using the short interference. This means that allusion basically describes one thing by talking about one thing while thinking of another. In Act V Scene I, Shakespeare uses allusion to explain how Antonio saved Viola's life.
SEBASTIAN... Let fancy still my sense in Lethe steep.
If it be thus to dream, still let me sleep!
The example above represents a personification.
Personification is a literary device that is used to attribute human characteristics to non-human beings, inanimate objects or abstract ideas. In this case, Sebastian uses personification to express describe his feelings about the fact that Olivia is in love with him.
DUKE: Methought she purg'd the air of pestilence,
That instant was I turn'd into a hart [deer];
The example above represents a metaphor.
The metaphor represents an indirect comparison between two things, based on at least one similarity between them. In this part, Shakespeare uses metaphor to compare Duke Orsino with a deer at the moment when he saw Olivia.