While racials are a nice bonus, they can weigh heavily on your racial decision when rolling a given class. For example, many Horde warriors roll Tauren because of the 5% health increase. This conflicts with rolling the race that you'd prefer combined with the class you desire.
There has been much speculation about what it would be like to be able to choose your own racials, and reader Mike even came up with a talent tree method for doing just that.
If you were given the power to choose, which three or four would you choose, and why? Keep in mind the overall balance which generally includes a passive ability, an active one, and one or two minor buffs to stats such as resistances, health, or professions.