Easy, now especially in a disparaging sense; contemptibly easy.
Lazy, simplistic (especially of explanations, discussions etc.).
Effortless, fluent (of work, abilities etc.).
Of a reaction or other process, taking place readily.
A person who accomplishes tasks with efficiency and grace, especially one with verbal skills who is persuasive in interpersonal relationships, negotiation, etc.
A skillful, manipulative person, con artist, or clever scoundrel.