Anti-Hero: He became this because of his early treatment.
Battle Couple: With Raphtalia
Can't Stand Them, Can't Live Without Them: How he views the other Heroes. He can't go back home unless they finish their mission to stop the Wave Invasions.
Combat Pragmatist: A necessity when most of his attacks are effectively useless. Can't attack? Lob monsters at them.
Cherry Tapping: Naofumi's attack with the Balloon monsters that latch onto him early in the story.
Counter Attack: Naofumi's only way to deal damage, justified in that his only weapon is his shield, and his attack stats are very low that he have spent minutes striking starting level mooks if he wanted to kill by his own hand.
Deity of Human Origin
An Entrepreneur Is You: Since he gets the bare minimum of official funding, unlike the other Heroes, Naofumi resorts to manufacturing potions and peddling to get by. This turns out to his benefit later on.
Heart Is an Awesome Power: As it turns out, his shield allows to boost his party's stat and EXP growth so that they eventually become stronger than the other heroes
Heroic RROD: After he used his Shield of Wrath, he is bedridden for a few days and his stats aside from his defense are greatly reduced
Hero with Bad Publicity: Played with and then ultimately subverted. While the nobility and other heroes hate him at first, the fact that he's the only one doing a proper job of protecting the peasantry makes the people love him. Once the queen returns, the truth about him is revealed and his reputation gets even better.
Jade-Colored Glasses: Sees everyone out to get him and that the only one he can trust are slaves after what Malty did to him.
Locked Out of the Loop: All the other heroes got money, status, party members, and information - Naofumi had to learn the hard way or by the generosity of a few individuals.
Naïve Newcomer: Initially this, but due to Malty's actions, he became a very cynical and jaded individual.
Never Gets Drunk: and never gets seasick either. It's part of his secondary power that all the heroes have. He could eat a fruit that needs to be heavily diluted before it could be served as a liquor; Motoyasu took a bite and promptly fainted while Naofumi continuously ate like a snack.
Oblivious to Love: Thanks to Malty's betrayal, he cannot see Raphtalia, or rather anyone's affection towards him.
Physical God: Naofumi eventually becomes this along with Raphtalia
Power at a Price: The Shield of Wrath evokes this. Read Heroic RROD.
Rape Is a Special Kind of Evil: What he is blamed for. Turns out to be a ploy from the very beginning to publicly undermine the Shield Hero.
The Scapegoat: After being framed, Naofumi becomes this for the King, being blamed for nearly everything bad or wrong that is happening because of the Wave invasions.
Stone Wall: Standard as the Hero of the Shield.
The Power of Hate: What his Shield's Cursed Form runs on.
The Un Favourite: The Hero of Shield, and Naofumi by extension, is treated as being inferior to the other three Heroes.
Unwanted False Faith: The regular people call him 'Saint Shield', and the Demi-humans revere him. His new cynical outlook on life makes this a situation he'd rather not have to deal with.
Unwanted Harem: So far includes Raphtalia, Firo, Melty, and still growing.
What Kind of Lame Power Is Heart, Anyway?: The general view on the Hero of the Shield by the other Heroes.
With Great Power Comes Great Insanity: If it weren't for Firo, this would occur when Naofumi uses his Wrath Shield