My top two are The Smiths and New Order.
When I was in High School I had a neighbor that was a tall, beautiful, introverted, swim team, Smiths fan. My friends and I just didn't get it, but all the cool girls loved him. It was years before I *got* the Smiths, and suddenly then my old neighbor.
When I was at college, I had a guy who lived in the room next to me in the dorm sophomore year. His name was Mike. In their room Mike and his roomate had bunk beds in which Mike held the bottom bunk. One night the entire floor was awakened to Mike's screams when the top bunk collapsed on top of him in the middle of the night. He was OK, but from that time on we all called him "Sandwich Mike". Anyway, Mike had a page boy haircut and really loved New Order. Being the freedom rockin hippy that I was, I didn't *get* it, but now, listening to their great bass lines I totally understand. (although I would like to add that the gap between the songs that I think are great and the rest is pretty large.)
So who is the best band you were surprised to discover you liked?