Most effective playerFollow

I am fairly new to WoW, and wanted to hear what everyone thinks about which character is the most effective for different types of game play. I realize this may be a little bit broad, but really would just love to hear about your experience with different characters trying to build different aspects of that character. So tell me what you all think! Game on!

I would say it depends on the patch, things are always changing and being re-balanced. Play what interests you.