I'm a sucker for the Swashbuckler shirts! For one thing, they tend to look better with the midriff-baring armor that seems to dominate the lower levels (was pleased to find in Northrend that they're more practical with their armor!), but also, my nelfs look really cute in them. The red one with the black tuxedo pants is really nice.

My favorite outfit, though, I think, is a fishing outfit I gave my hunter for a while, until I got tired of having to save bag space for her regular armor -- blue overalls that my mage made for her, a "loosely threaded hat" she picked up somewhere, and knitted sandals. Comfy and cute!