As a DM, I try to strictly avoid giving the party an NPC who 'leads' them.
I often have a 'Giles' figure, but that's just to get the party started, and he rarely stays around in the campaign.
In the past, I had a problem with no PCs coming forward to lead - and democracies don't work well in a dungeon environment. But in my latest two campaigns, a leader-type character has stepped forward. Even better, in my email game, they seem to (unconsciously, I'm sure) look to different characters depending on the situation (which gives everyone a chance to be leader). Still, they're very disorganized in combat.
For the record, I voted cleric, because in both my games, a cleric is looked to the most.