* Descriptive: The iridescent green slug left a shimmering trail across the damp pavement.
* Humorous: After a long day, all I wanted to do was curl up with a good book and a big, juicy slug. (This is a play on words, as slugs are not typically considered edible).
* Action: He aimed his foot at the slug, hoping to squish it before it reached the lettuce.
* Figurative: The traffic moved at a snail's pace, or rather, a slug's pace.
The best sentence will depend on the context and the desired tone.