Mania posted about a tip from Lienna about spamming Wing Clip to powerlevel weapon skill, and I've confirmed that yes, as long as you wait for the global cooldown (obviously), you an spam Wing Clip and you'll receive weapon skill ups for those hits. Though I didn't try it with any abilities, I'd assume that it works for any instant melee hit (Sunder Armor jumps to mind). Of course, you not only have to worry about hitting whatever it is you choose to hit, but you also have to worry about killing it-- I did have to step back and finish off the mob with my hunter's bow.
So it seems hunters can level their weapon skills a little faster than other classes. And why shouldn't they? They have a lot more weapons to skill up, and it's not like melee weapon skill matters much to hunters anyway, except at the very limits of min-maxing. A melee hit is a melee hit-- if hunters get to hit more often, then they get to level weapon skill faster, too.