I feel like I won't be able to contain myself to three...I'm putting aside all music that reminds me of my dad in terms of nostalgia - jazz, musical theater, etc - big influence in my musical education/love and fills me with nostalgia, but for the purposes of this question...
U2 - "Gloria" - Reminds me of walking to my friend's house in a big group in Jr. high to watch MTV - first music that I loved that was NOT influenced by my older siblings - not to disparage all the music my older sibs introduced me to...
Van Halen - "Ain't Talking About Love"/"Feel Your Love Tonight" - every high school party I ever attended*...
Dave Mason - "We Just Disagree" - Fills me with nostalgia for the beach resort restaurant that I worked at for summers all through high school/college. They were like a family to me and we still keep in touch. They played easy 70's hits in the dining room, like this song, however, I could substitute Gordon Lightfoot, Seals and Crofts, Tavares, etc., hard to pick one...
*So, funny story...my daughter has me watching this kids' Baking Championship with Valerie Bertinelli as a judge. One Episode, Valerie mentioned Wolfie, and my daughter was like, "Who's Wolfie??" so I tried to explain Valerie's tv career/marriage to Eddie Van Halen - who my daughter had been listening to with me for many years. Mind blown!