My first favorite ABBA song that I ever heard was "Waterloo" when it was featured on the movie, "Muriel's Wedding" and a short clip from "The Simpsons". My wife introduced me to "Mamma Mia" a few years ago and have come to really like "Under Attack" and probably listen to that song the most out of any of them, particularly the original cast recording of it from "Mamma Mia". "SOS", "Knowing Me, Knowing You," and "I Have a Dream" are some of my other favorites. Heck, pretty much darn near all of the songs featured in "Mamma Mia" were great. It's actually kind of hard to think of one favorite song from their catalog that I've listened to so far although I don't listen to Fernando (sp?) nor Chaquiqita (sp?) much. I don't understand the hatred and derision that some people exhibit towards their music and/or people who enjoy them.