Solstice Knight

The Solstice Knight is... technically... a Paladin Variant Class for Dungeons & Dragons 3rd Edition in Dragon Magazine #338. Why technically? Because the Solstice Knight is actually handled as a set of substitution levels rather than a full-fledged class. Lore-wise, these are paladins, most obviously ones in service to solar deities like Pelor or Lathander, who have undertaken a special role in holding the sacred vigil held during the winter solstice and thus found themselves rewarded with abilities unusual compared to more mainstream paladins.

Mechanically, a Solstice Knight is a paladin who "swaps out" their regular paladin class at either level 3, level 5, or both, which alters their class abilities.

If the paladin takes the Solstice Knight version of 3rd level, they lose the Divine Health feature but gain the Spell-Like feature of Blessed Radiance, which lets them cast Daylight (centered upon themselves) with a caster level equal to their paladin level. Blessed Radiance can be invoked times per day equal to the paladin's Smite Evil uses - no, you don't sacrifice Smite Evil uses when you invoked Blessed Radiance, its just their uses per day totals are the same.

If the paladin takes the Solstice Knight version of 5th level, they lose one of their Smite Evil use boosts (so they will forever after have one less Smite Evil per day compared to a regular paladin) but in return they gain Darkvision +30 feet (so if they had Darkvision before, it increases by +30 feet, and if they didn't have it, then they gain Darkvision 30 feet) as well as Strike of the Faithful, a Supernatural Ability which means the paladin's Smite Evil does double damage to evil-aligned undead.