For me it's 2.
My dad died a week after my 12th birthday and I was not diagnosed autistic until I went to uni so I was very young for my age. So for me it's Paul Simon 'father and daughter' which ironically was created for the wild thornberrys movie the year he died and it just spoke to me. It wasn't until I was 14 that he released it as a single and I heard it on the radio and then bought the cd (2004) that I could listen to it and cry because I lived my dad so much and I knew he loved me but when I heard this song it made me certain he really did love me. It's hard to explain.
Secondly it's elbow's 'one day like this' it just sang to me, I used to dry my hair to this song and just lose myself in it during uni. It really really helped me with my grief that I have to say Took far longer than my mum to deal with, it was like with every year I understood more what it was to lose a parent and the reality of it. It also coincided with a difficult break up and it helped me realise who I was, and that I deserved far more.
I'm now 31 and my dad would be proud of me I think. It's funny how things work out.