When you first get World of Warcraft, staring at the race/class selection screen can be a daunting task. There are so many factors to choose from, and you're unlikely to know anything about how the classes really function besides what you read in the manual. And, as you can see by the many people who start out arguments with "I rolled a ____ because the character description said ...", you can sometimes be horribly mistaken about what your class will end up doing.
My first class ended up being a druid because "I can be a cat! Cool!" Unfortunately, I was so scared of wasting mana that I hit everything with my staff and quickly grew bored. Also I thought Teldrassil was the entire world and that I was almost finished with the game. After learning a bit more about the game, I rolled a paladin because I could do damage and heal myself. That got scrapped around the time the damage began looking ... not so hot.
Finally, my friend's enticements to join the Horde grew too strong to resist. I rolled a rogue for two reasons: I could hide instead of fighting things, and I could steal stuff from people. I also decided on a troll because troll females stand up straight and have mohawks. (Ah, the days before everyone rolled undead for Will of the Forsaken!) As I leveled to 60 and raided MC, BWL and AQ40, I discovered that hiding and stealing may not have been the best reason to roll a rogue. The Twin Emps do not work well with pickpocketing.
Other classes, such as druids who want to use their hybrid skills in raids and paladins who bemoan their lack of tanking abilities, claim they were misled at character selection. Why did you pick your character's race and class, and do you have any regrets?