Sometimes the atheist at a funeral is at a disadvantage.
The believer can come forward and say something positive like the decedent has gone to be with Jesus.
The best the atheist can do is say nothing or "when you die you rot."
I think our freethought tradition offers a rich assortment of responses.
1. "Van Halen is dead, too." (Or whatever celeb just died. But avoid the less famous, like Norm Crosby. It really is awkward to have to give the back story.)
2. "At least he/she isn't praying for recovery anymore."
3. "Please accept the corporate sympathy of America's atheists." (Okay, save that one for Trump's sendoff.)
4. "At least now he/she knows that there's no afterlife. Or, no, actually, with a dead brain, he/she doesn't know anything."
5. "It's all a journey. Is this thing catered?" (For multi-tasking atheists)
6. "Let's us do an experiment and leave a cell phone in his/her hand."
7. "It could be worse, you know. If there was a heaven, he/she would probably be listening to George Beverly Shea singing endless songs. If there was a hell, it would be an eternal Trump rally."
8. "You know, Jesus lived in the pre-Lysol days and was probably crawling with cooties."