General synonyms:
* Charming
* Sophisticated
* Elegant
* Suave
* Gallant
* Polished
* Dapper
* Handsome
More specific synonyms:
* Rakish: Implies a slightly roguish or carefree charm.
* Affable: Highlights friendliness and ease of manner.
* Urbane: Emphasizes polished manners and social grace.
* Courtly: Suggests a formal and dignified elegance.
* Dashing: Emphasizes a bold and confident charm.
* Alluring: Highlights attractiveness and allure.
The best synonym will depend on the specific context and the particular aspect of "debonair" you want to emphasize.