Formal/Literary:
* Despite the horrific scene unfolding before him, the detective remained impassive, his face a mask of stoicism.
* The statue stood impassive, its cold, marble gaze fixed on the endless horizon.
Descriptive:
* Her face was impassive as she listened to the news, giving no hint of her inner turmoil.
* The mountain stood impassive, its snow-capped peak unyielding to the wind and the storm.
Figurative:
* The old clock ticked impassively, oblivious to the frantic passage of time.
* The law, in its impassive justice, had no regard for individual circumstance.
Contrastive:
* While the crowd was filled with passionate pleas, the judge remained impassive, listening with a detached air.
* The children were full of energy and excitement, while their parents watched impassively from the sidelines.
Remember that "impassive" implies a lack of emotional response, often to the point of seeming indifferent.