Disclaimer: They aren't mine, they're Paramount's.
We laughed when he sang for our wedding present. Little did we know it would be the last time Data celebrated. In retrospect, it was the best gift he could've given us. No physical gift would be quite as poignant as the last wonderful party. Our wedding celebration. When we look back and remember that spledid gift, we remember how thoughful and caring an individual he was. We see how far he came from fifteen years ago, when he couldn't whistle. He was singing, and nobody will ever forget the sound of his voice as he sang to us.
Data was a child in many ways when we first met him. We got to watch him grow and become ever closer to his goal of being human. It was a privilege to encourage him along the journey. Perhaps, in his death, he finally realized humanity. For immortality, not a positronic brain or superhuman strength, was the least human of all his traits. Some consolation may be found in the fact that Data died more human than most people believed possible.
There are some who may question whether a machine can have a soul, a spirit. It's awful to think of Data just vanishing into oblivion, and perhaps that drives us to believe that it is possible for any sentient being to have a soul. It is comforting to think that perhaps he has gone on to join Tasha.
Yet Data can never vanish. He can never become oblivious as long as we remember him, and keep his memory close to our hearts. And when we die, his legacy will remain. Children will be tought how he saved us, how he saved Earth. We will make sure they never forget.
Data used to ponder what immortality would be like. He used to wonder what it would be like to see all his friends die, again and again. Instead, it was we who survived him. He will never suffer the pains of immortality.
He had as much of a conscience as anyone. In fact, he had more of a conscience than some flesh-and-blood humans. He knew when all was said and done, he had to be able to live with himself and what he'd done. Data saved half the Fleet, then submitted himself for disciplinary action for disobeying orders! He was willing to risk deactivation to do right by the Ba'ku. He wanted to better himself, to become more human, but he refused to do it at the expense of others. He was noble, putting himself last always. Data was extraordinary.
Data's wedding gift to us was a song. But his ultimate gift to us was life, and a better appreciation of it.