Each had a stupid half grin on his face.

The right side of his mouth tipped up in a half grin.

One corner of her mouth quirked into a half grin.

He squeezed back a little too hard, giving me a half grin as he did.

But he has an unpleasant half grin on his face that Vera doesn't care for.

He gave her a first half grin, the one she remembered.

But then a half grin formed as he added, "I don't always take good advice."

"Hi, there," Tom said, with a half grin in answer to her question.

He hung up and managed a half grin at me.

She looked aside at him, and managed to muster up a half grin.