Assuming you're playing 4E, any warrior whose actions are determined by total faith (faith in god, nation, or organization) will suffice. As long as the character is willing to sacrifice himself (and anything/everything else) for that faith then you're good to go--that's the kind of selfless devotion that defines a paladin.
Captain America, Superman, and Batman are fine examples of heroes motivated by ideals (as opposed to personal profit). Sturm, from the age-appropriate Dragonlance series, is perhaps the finest example. Harry Potter is arguably being groomed by Dumbledore in Paladin ideals.
If you're playing 3E or earlier, there's a "Paladin's Code" and the Lawful Good requirement, which makes things much more specific & limited. You've got Joan of Arc and you've got Lancelot (a particularly good example because he falls when he breaks his code).
Speaking of fallen paladins, Anakin Skywalker in Episodes 2 and 3 is a perfect example of the fall of a 3E-style paladin / rise of a 3E-style blackguard.