As a noun:
* The artist used great subtlety in her brushstrokes, creating a sense of depth and texture. (Describes the artist's skill)
* The detective noticed the subtle shift in the suspect's demeanor, a clue that something wasn't right. (Describes a small but important detail)
* There was a subtle irony in the way he treated her, praising her work while secretly undermining it. (Describes a nuanced irony)
As an adjective:
* The film's ending was subtle, leaving the audience to ponder its meaning. (Describes the style of the ending)
* The subtle changes in color across the landscape were breathtaking. (Describes the nature of the color changes)
* She made a subtle comment about his weight, hoping he wouldn't notice. (Describes the nature of the comment)
Remember, "subtlety" refers to the quality of being delicate, understated, and often requiring careful attention to be noticed.