My current campaign has a gnome paladin mount on a (winged) 1/2 celestial riding dog. The flying and small size (and no reach with an undersized lance) facilitates getting into a charging position, and ensures that the mount can enter any environment.
A ring of spell-storing allows for a true-striking, power-attacking, smiting, spirited lance charge.
Other charging builds have included a Paladin of Wee-jas that could cast his own true-strike and could thus perform this trick as early as 3rd level.