So, there are basically two paladins that I've played or DMed as NPCs, off-and-on, in different versions of D&D and even different rules systems and even different media (like, for instance, I'm currently playing as one in a game of Mount and Blade
The first is a character I created with my brother, years and years ago, named Azdrinac Lichbane. He comes from a long line of more-or-less holy knights who have been pledged, for all eternity, to stand against the undead. In a Forgotten Realms campaign, he'd be a Paladin of Kelemvor; in Eberron, he's probably a hard-line follower of the Silver Flame. He's a bit battered, and a little fatalistic - he knows that he was born for a purpose, and his children after him (should he survive to have any), will also be born for a purpose; it is unlikely that he will ever actually complete his divine charge, and he knows it. He existed before I read the series, but John Ross from the Word and Void
novels by Terry Brooks has a lot in common with him, as well as Sparhawk from The Elenium
. He doesn't wear perfect, shiny armor, because his favored set is a hand-me-down that has been in the family for centuries, and shows the dents, patches, and repairs attendant thereto.
Secondly, I have Rolndo of-many-last-names, who I started playing in 3E as a Paladin / Rogue of Yondalla - a "knight in shining leather armor" by way of Guybrush Threepwood. He's obviously been with my a lot shorter time than Azdrinac, so he hasn't found his way into nearly as many campaigns, but I like him anyway. Yondalla is the matriarch and protector of the halfling family - and her paladins, to me, take on a similar role; many of them expanding on the concept of the family to include the friendly races as honorary cousins. Rolndo always has a twinkle in his eye and a bounce in his step - and he smiles because he knows the absolute gravity of his responsibilities, and you have to either laugh or cry, right? So make the best of it, and maybe you'll get everyone else to make the best of it, too.
Azdrinac's the type who would hold a castle wall by himself against an assaulting army, giving the women and children a chance to escape, because he knows he has been chosen for exactly this - and though he wouldn't ask, he'd welcome anyone who wanted to stand with him.
Rolndo would have the whole town convinced to take to the walls themselves and stand together against the invader.