"My Lovely Man" - Red Hot Chili Peppers... originally written as a tribute to thier original guitarist Hilel Slovak, it's a great song about missing a close friend, and they play it with such heart.

or

Boards of Canada - "Dayvan Cowboy" ... the song is just fucking beautiful, and when the cymbals come in with the reverse delay sounding like waves crashing... this song always calms me down, no matter how stressed, angry, sad or depressed, so I imagine if played at my funeral, the same calming reassuring effect would help my freinds and family get over mourning. and just cause I fucking love this song.