Going out with a smile. Christopher Eccleston will always be my favourite.
He made sure the last thing Rose saw of him was his smile. He was so careful not to scare her. Playing along and pulling jokes until the last moment.
He knew she was terrified, confused, she didn’t know what was happening and it was so unexpected to him that he hadn’t had time to explain regeneration to her before it happened.
He never got the time or the courage to warn her, to sit her down and go “listen, Rose, I don’t die, I regenerate. And it could be scary to look at, so you need to be prepared"
So when it finally happened, when he couldn’t delay explanations any more, he tried to make it the less traumatic as possible to her. He jokes about his “daft old face" and tries to make it look less painful than it actually is, so that she doesn’t need to be more terrified than she already is.
Final, ultimate proof of his love for her.