I do like to think of this sometimes, though if I do have to have a funeral is much rather it just be an informal gathering of a very select few, with no speeches or readings or any of that. That being said, it's not for me to decide how those left behind grieve me, ultimately.
It's kind of hard to pick individual snippets, because I primarily listen to classical music, and I don't want my funeral to last 16 hours just because I wanted the entire Ring cycle to be played. The people are grieving enough as it is. It's limiting to try to choose even individual movements or arias of greater works that don't take ages. I'm very far from religious, but there's one movement from a Mozart mass that I've absolutely loved ever since I first heard it. I don't personally stand behind the meaning of the text as an atheist, but if there were some kind of a soul left behind after death, I'd feel some sort of contentment hearing this as I drift away from the funeral proceedings:
Unfortunately that's not the specific recording I want, as it's not on YouTube that I can see (Sir Colin Davis, LSO, 1971). But it's a banger and I'd like it to be a reminder to those present that there were good times we had shared, in the past.