Oh man, that's a hard question. I love so many different songs for so many different reasons. I can literally remember every event in my life based on the song I associate with that time period. So I'd have to break my favorite song answer into a few age groups.
Birth to 5 yrs old- Hotel California by the Eagles (Mom was a hippie)
5-10 yrs old- Whip it by Devo ( I liked to roller skate, that happened to be a hit at the rinks)
10-12 yrs old- Borderline by Madonna ( I thought she was so everything I wanted to be when I grew up lol haha how that would change!
12-15 yrs old- Once bitten twice shy-Warrant
15-20 yrs old- Shook me all night long- ACDC
20-25 yrs old- Run to you by Bryan Adams
25-30 yrs old- Sing for the moment-Eminem
30-35 yrs old- Steamroller-James Taylor
35-40yrs old- All summer long -Kid Rock