depends....i've been really into flat bars lately, but i also love nitto 021s. i also just picked up some cruiser bars...ah...yeah, humangirl already said that. i also have some rando bars that i like, but haven't used as much, risers on the mtb.
but, yeah, i switch it up from time to time...different things will make you ride differently, so you switch depending on feel, the needs for what you're doing (working, touring, cruising, barhopping, whatever)...