In rhetoric, a rhetorical device or resource of language is a technique that an author or speaker uses to convey to the listener or reader a meaning with the goal of persuading him or her towards considering a topic from a different perspective.
The goal of rhetoric is to persuade towards a particular frame of view or a particular course of action, so appropriate rhetorical devices are used to construct sentences designed to encourage or provoke a rational argument from an emotional display of a given perspective or action. Note that although rhetorical devices may be used to evoke an emotional response in the audience, this is not their primary purpose.
Logos is the use of logical ideas to appeal to the audience.
Pathos is an appeal to the audience's emotions.
Ethos describes the guiding tenets that characterize a community, nation, or ideology; it may also appeal to the authors credibility.
Irony and metaphor 
The use of irony in rhetoric is primarily to convey to the audience an incongruity that is often used as a tool of humor in order to deprecate or ridicule an idea or course of action.
The use of metaphor in rhetoric is primarily to convey to the audience a new idea or meaning by linking it to an existing idea or meaning with which the audience is already familiar. By making the new concept appear to be linked to — or a type of — the old and familiar concept, the person using the metaphor hopes to help the audience understand the new concept.
An example of rhetorical device is this passage attributed to a speech by Abraham Lincoln about a political adversary in which Lincoln said that his adversary had "dived down deeper into the sea of knowledge and come up drier than any other man he knew".
This attributed quote uses a body of water as a metaphor for a body of knowledge with the ironical idea of someone who gained so little from his education that he achieved the impossible of jumping into a body of water and climbing back out without getting wet.
Sonic devices 
Sonic devices depend on sound.
- Alliteration is the use of a stream of words with the same first phoneme, only interrupted by grammatically required words (e.g. a(n), the, to, for, by, etc.). It is used for emphasis, suggesting a humorous or even threatening tone..
- The zoo kept several selfish seals.
- I hate that heartless heathen.
- Assonance is the repetition of a similar set of vowel sounds. It is used to emphasize intensity, mood, and imagery, among others.
- Cacophony is the use of words with harsh consonants, usually at the beginning of a word.
- Onomatopoeia is the use of words that attempt to emulate a sound. When used colloquially, it is often accompanied by multiple exclamation marks and in all caps. It is common in comic strips and some cartoons.
- smek - high-fiving someone; smacking someone in the face
- thwap - lying down carelessly; dropping a pile of papers or books carelessly
- kaboom - exploding
- ding-dong - ringing a doorbell
- plop - sitting/lying down carelessly (also a verb: “Plop down on the couch.”)
- bang - exploding; shooting a powerful gun
- badabada - operating a (semi-)automatic machine gun (mainly in comics)
Altered signification devices 
Devices of altered signification shift the meaning of words.
- Metaphor directly says something is something else. For example, "his beard was a lion's mane".
- Simile is a gentler form of metaphor which tends to use "as" or "like" to compare something to something else. For example, "his beard was like a lion's mane."