For mountain bikes it's easiest if you pick bars that you can use with the existing brake levers and shifter, although that's not to say you have to. The original moustache bar was made for a mountain bike after all.
By Far and away the most popular is the Soma Oxford. It's based on a classic design and offer a generous back sweep and an a small amount of rise.
In the same vein the Sycip Wonder Bar and the Nitto Albatross offer similar positioning.