A thing that represents itself and something else – symbol. An example would be the dove, or the colour white, symbolizing peace.
One thing IS another – metaphor. What distinguishes the metaphor from the simile is that the metaphor is directly introducing the imagery in the text without a comparison word. An example would be: "he is such a pig."
One thing is like another – simile. The simile introduces the comparison with a word such as "like" or "as." "He eats like an ogre" could be an example.
Mental pictures created through descriptions which appeal to the senses – imagery. In literature, the purpose of imagery is to enrich the text by enabling the reader to picture elements of it in their mind.
Use of one word in place of another word associated with it – metonymy. A common type of metonymy is the designation of something by where it is contained, for example "the White House" for the President's administration.
A word which imitates a sound – onomatopoeia. Such as woof, crack, bang.
Exaggeration – hyperbole.
Apparent contradiction – paradox.
Repetition of initial consonant sounds – alliteration. This is often used in poetry, but also in prose, to help the reader imagine the sounds of the scene which is being described (like lots of Ls when writing about water, or Ss when writing about a snake).