* Confident and amused: "He smirked, knowing he had won the argument."
* Sarcastic and condescending: "She smirked at his attempt to impress her, finding it utterly pathetic."
* Playful and flirtatious: "He smirked at her, running a hand through his hair, hoping to catch her eye."
* Sly and mischievous: "The cat smirked, knowing it had just stolen the cream from the counter."
* Triumphant and arrogant: "He smirked, having achieved his goal at everyone else's expense."
Remember, the context and tone of voice will greatly influence the meaning of "smirk".