* A known, insignificant issue: Something like "(!)minor dent on bumper"
* A subjective opinion: "(!)Needs some TLC" (Tender Loving Care)
* An extra detail to differentiate from other similar models: "(!)Premium Sound System"
Essentially, the person who wrote the description used the (!) to draw attention to something they deemed important, but not critical, in their listing or note. You'd need to see the full context to understand its precise meaning.