If you want to write an obituary with humor, tread lightly. When done well, it can be a fun and loving tribute to a person who appreciated a good joke.
But not everyone can pull off humor in an obituary. When done poorly, it will come off as distasteful and disrespectful. If you want to write an obituary with humor, write from the heart and keep it a loving tribute, not a roast of the deceased. This site has some great examples of obituaries written with humor. Good luck!