If you want to breeze through World of Warcraft, then I’ve got a quick news flash for you. Level a hunter class. Doesn’t really matter what race, but once you get to level 10 and train your faithful pet, you’ll be a leveling fool!
My Orc hunter is level 12 already, with my little bit of play time, and if I could sit down for a whole day, uninterrupted, I would be probably be able to reach at least 22.
Other than a hunter, I’d say your next best bet to quickly zoom through the leveling process would be a death knight. Especially if you went with enough points to get you a full-time ghoul pet. Aside from the DK’s ability to generate health out of damage dealt and honor/experience kills, they’re pretty unstoppable. No down time on either a dk or a hunter, as your pet does most of your damage while you stand back and auto fire with a bow/gun for the most part.
If you want to get into WoW, or just give it a try, go for the easy Win. Of course, dk’s are only available once you get a character up to level 55, but if you level a hunter, it’ll still fly by.