Emily Dickinson's "My life had stood--a Loaded Gun" contains one main hyperbole. A hyperbole is an obvious exaggeration made by an author (in literature) to emphasize something. In some cases, hyperboles can be metaphors (which provide a comparison between dissimilar things). In this case, an author may provide a metaphor to exaggerate the existence or being of something.
In the case of the poem, Dickinson uses metaphors to illustrate the exaggerations. The speaker's life is ready to explode (not literally, but figuratively). This image is created by the metaphor of the speaker's life to a gun. The poem, one long extended metaphor, stands to exaggerate on how the speaker's life is like a gun.
The speaker has the ability to be carried away, hunt, roam, and take the life of another. Although not defined as a specific hyperbole, the comparison of one's life to a gun can be identified as an exaggeration in its own right.