People have been complaining about the lack of character customization in WoW for a long time now. I agree that the character creation screen in WoW does seem a bit limited when the customization options in other games can generate thousands of permutations, but for now, I'm content with the way things are. Why? Because a lot of the time, my character doesn't even look like himself.
I have some 30 vanity items that transform the appearance of my main character or the world around him, and I put them to good use. Whether it's clucking my way through city streets as an Arakkoa (via my Time-Lost Figurine), or popping my Iron Boot Flask and making everyone in the Auction House dance with me (via my Piccolo of the Flaming Fire, I love being able to change the way I look when I get sick of the same old character model. I've learned that dropping my Tol Barad Searchlight in a capital city almost always generates a party out of thin air as passersby use their Mylune's Call, throw down their Haunted War Drums, set out their Romantic Picnic Baskets, and decorate with their Guild Battle Standards.
But while I use them to escape the tedium of limited character customization, vanity items for some players serve loftier purposes. Back in Wrath, a guildie of mine would always use a Gordok Ogre Suit when he thought the next attempt would be the one in which we'd finally down the progression boss we had been working on all night. Whenever we saw that ogre, we knew things were getting serious and that a boss kill was imminent.
So how do you use vanity items? Which is your item of choice when transforming the appearance of your character?