Apart from the Mozart mentioned above, it seems to be more my attitude towards instruments that changes with a live performance. Flute as also mentioned above, and watching the Proms tonight also reminded me about percussion.
You don't really get the full benefit of percussion on radio or CD. But watching percussionists in a live orchestra can be thrilling! I remember one particular drummer in the orchestra from Sofia, Bulgaria. Instead of keeping her elbows close in and being quite "dignified", as seems to be the norm, she was really giving it seven bells, both arms stretched wide out and bashing away as if her life depended on it. There was an electric atmosphere that night, full of exuberance, and I remember thinking, "wow, I want to play the drums, it looks so exciting"!
And piano - I can't say I'd ever been a particular fan of the piano until one night when I saw Anna Markland, past Young Musician of the Year, perform Gershwin's Rhapsody in Blue. It was spellbinding. Her hands were moving so fast that you couldn't see them, and I remember "welling up" several times, not because the music has any association for me but because it was simply a magical performance. I've seen Rhapsody performed many times since, but Anna Markland's performance has never been bettered. That performance opened my eyes to the piano, and I've enjoyed listening to it every since.