Well, I really like the Holy Trinity of the Paladin specs: Tank, DPS, and Support/Healer.
As the RPG Paladin (DnD for example), you can play in whatever role that is needed, for me it's just fine for a Paladin.
One only different spec that pops in my mind at the moment is maybe a caster DPS, using holy spells, but I believe that should be more a spec for a Priest. I don't like the idea of a Paladin stealing the thunder of a Priest as a Holy Caster DPS.