General synonyms:
* Cunning
* Sly
* Shrewd
* Astute
* Devious
* Artful
* Crafty
* Guileful
* Machiavellian
More specific synonyms:
* Tricky: If you want to emphasize the ability to deceive.
* Resourceful: If you want to highlight their ability to use their skills to their advantage.
* Clever: If you want to emphasize their intelligence and ability to outwit others.
The best synonym to use will depend on the specific situation and the nuance you want to convey.