My personal favorite kind of changes. I know what I'd answer if someone asked for my top five favorite songs of all time (below) but a sort of "personal favorite"? I don't think I could name one.
"Evidence of Autumn", Genesis - to this day reminds me of my college girlfriend. I don't miss her in the sense of wanting to be with her, but she reminds me of a better time and a time of growth, so I think of her a lot.
"Drops Of Jupiter", Train - reminds me of a crucial point in my first marriage (that ultimately ended). We rebounded, briefly, from her "looking for herself out there", and that period was one that changed my life forever.
"Tonight", Ozzy - I don't know; I just love the lyrics, that to me point to a sort of personal strength and personal resilience. Yeah, everything is bad, I'm feeling down, but tonight, tonight, it's going to be special. And that solo is just redemption personified.
"Me And Bobby McGee", Kris Kristofferson - my dad's favorite song is Kris's "Sunday morning Coming Down" but this was one of the first songs he ever played for me, and that wasn't really something we shared. It was a great insight into him and now it's a symbol of what he meant (means) to me. I'm thinking of doing a couple three songs at a local bar open mic night, and this will certainly be one of them, if I can get past the "and somewhere near Salinas, Lord, I let her slip away, looking for the home I hope she'll find" line without crying like a toddler.
For the record, if asked, I usually list "Good Vibrations" and "A Day In The Life" as the two greatest songs of all time.