Simple:
* The child stared intently at the magician's tricks.
Descriptive:
* The detective listened intently to the witness's testimony, searching for any inconsistencies.
Figurative:
* The artist gazed intently at the canvas, her brush poised to capture the essence of the scene.
Action-oriented:
* She read the letter intently, her brow furrowed in concentration.
Emotional:
* He looked at her with an intense gaze, his eyes burning with a mixture of love and longing.
The best sentence will depend on the specific context and the desired emphasis.