I don't like to nominate "the best" or "favourite" things as they change for me so often and I have so many...BUT two opening licks stand out for personal reasons.
The Animals-style intro to House of the Rising Sun reminds me of my Greek friend Yorgos, as when he starts off with that it means he's finished serving for the night and its time for me to earn my free brandy. The other is one I mentioned here recently: the intro the Inkspots used on so many of their recordings. I hear it and launch into what I guess will come next. That means I'm usually doing Whispering Grass while the Inkspots are doing something else entirely, but then I'm often singing something completely diferent to everyone else!
RtS (What you say, Hoppy? You told those babbling trees?)
PS Hi, MattR, welcome back.