In other words, do not include songs where the first time you heard them was the live version.
I am talking songs that you already knew and weren't that crazy about until you heard or saw a live version that made you really like it.
My picks:
Muse - Guiding Light It's still not even close to one of my favorite Muse songs, but I like it quite a bit now thanks to the Rome DVD.
Dream Theater - The Mirror/Lie Aside from The Mirror's intro (which I already knew from the Tokyo live video), I wasn't wild about either of these songs at first - believe it or not, they were still what I deemed "too heavy" for my tastes in late 1994 - but after seeing them live on the Awake tour, where they slayed, my tune quickly changed.
U2 - Lemon In the studio, it is kind of plodding and a but uninspired, but their shorter/more condensed and inspired version on the ZOO TV really made me love this song.