Which word suggests a demonstration of skill without effort?

The word "facile" refers to something that is achieved with ease and often implies a level of skill that appears effortless. When used to describe someone's abilities, it suggests that the person performs tasks or activities with such dexterity and grace that it seems almost automatic or without struggle. This term can connote a certain superficiality, as it may indicate that while the skill is evident, the effort behind it is minimal or not visible.

In contrast, "regale" means to entertain or amuse someone with stories or a feast, which does not inherently relate to skill or effort. "Redoubtable" describes someone who inspires fear or respect, typically indicating strength or formidable qualities, rather than effortless skill. Finally, "banal" refers to something that is overly simplistic or clichéd, lacking originality or freshness, and does not convey a sense of skill at all.

Thus, "facile" precisely captures the notion of skill demonstrated without visible effort, making it the most fitting choice.