Aww... this is a sweet thread. I like seeing everyone's "Our Song."
For me, we don't have one song that's "Ours" yet, but there are a handful that bring ktspktsp to mind immediately when I hear them:
Indigo Girls: "Power of Two"
Wilco: "Jesus, Etc."
Modest Mouse: "Float On" (or any of the first three songs on that album)
Sigur Ros: "Staralfurinn"
The Band: "The Night They Drove Old Dixie Down"
Anything by The Magnetic Fields
Anything by Drive-By Truckers
Bonnie Tyler: "Total Eclipse of the Heart"
Our favorite karaoke song!
Almost all of these are from the first few weeks/months of our relationship and hearing them brings back feelings from that time.
And then some of them are just songs that we ended up playing over and over again during long road trips, and became favorites for both of us (he introduced me to a lot of music).