Oh dear, this is difficult. I love singing along with, well, EVERYTHING! But Im gonna cheat again and choose 3 songs that I can help but sing along to. (HEY! be thankful that I didnt post every song Ive ever heard!)

The Imperial March by John Williams



Now I know this isn't conventional, choosing a song with no words to sing along to, but admit it. There is not one of you who upon hearing this song didn't start immediately going "DUN DUN DUN DUN DA DUN DUN DA DUN!"
...Yeah thats what I thought.

The Bitch of Living by The cast of Spring Awakening



Really this is representing every Broadway song known to man but this happens to be my most played of the genre and from my favorite musical, so the choice seems right :D
I can't recall how many times I have sung this song. I mean I would break my chair out and perform this in my living room even. Not to mention all the times sang in the green room or in the car. And I almost never sing the same part, god dont harmonies ROCK!

Belle by Paige O'hara



Like the previous song, this is representative of every Disney song known to man. I choose this one because I have often found myself singing along to this randomly. I remember walking in a field with Rachael singing at the top of our lungs, only to be interrupted y Jim and his dead baby jokes. Seriously though I sang this song a lot randomly with her and continue to do so with Shelby who is sweet enough to tell me I sound just like her when I know he is just being adorable <3