A Blood Elf Priest.

From a gameplay standpoint, I choose a priest for the character class. In a ROLE-PLAYING game, people play in groups and each person has a specific job to cover in order for the group to overcome challenges presented to them, in World of Warcraft's case surviving and beating down on wave upon wave of monsters and other uglies. WoW's (and any other RPG to date since Dungeons & Dragons) group dynamic has 3 major roles. Tank, the guy who keeps the group alive by directing as much damage as possible away from the group to himself. Damager, the guy who does the bulk of the damage to the enemy party. And the Healer, the guy who erases any damage sustained by the group. As a character class that works as a healer, I pick the priest because it's a big challenge to play (keeping 5 people alive and in working condition is much harder to do than it sounds), it's an important and relatively rare role (majority play as damagers for the sheer power trip of watching something crumple in pain to your 99999 damage strike), and there's a certain different feeling of accomplishment to being the one guy that everyone relies on to stay alive.

From an aesthetic standpoint, I pick female blood elf. Nope, the "I'd rather be looking at a girl's butt while playing" excuse doesn't apply here (though it would influence why I'd pick a blood elf female over, say, an undead or troll female). It's more of a chance to try and flesh out a concept character by bringing it out into an online rpg (for this character, it's a meek, naive girl trained by monks in the ways of White Magic).

That, and as one who grew up immersed in the Japanese Anime aesthetic of cutesy teenagers with big eyes, the blood elf is the only race that fits =)