Does Not Know How to Say Thanks

A character who doesn't know how to show their appreciation for something. Perhaps they have No Social Skills, or maybe their lives were so messed up that they simply don't know how thank someone because they never before experienced kindness or helpfulness from other people. Characters like this may give Disproportionate Rewards of some sort. Alternatively, they may do something they think would be a appropriate way to show their gratitude, only to shock or anger the person they were trying to thank instead.

Related to Cannot Spit It Out.

See also: Poisonous Friend and Rhetorical Request Blunder for other failed attempts at pleasing someone. See also Entitled Bastard for someone who rudely decides not to thank anyone. When it's a person suffering lack of gratitude, it's All of the Other Reindeer.

Anime and Manga

 * Gretel, one of a pair of truly Creepy Twins from Black Lagoon, does this to Rock when she tries to express her gratitude for being the first person who was nice to her and shedding tears for her because of the horrible things that she and her brother had been put through and how they chose to handle it, something that had been completely alien to her until then... by dropping her panties and sexually proposing to him. Rock is shocked and horrified and immediately leaves the room to go upstairs, where he proceeds to curse the men who caused her and her brother Hansel to become like this. Also a example of Evil Cannot Comprehend Good played for drama.
 * Nymph from Sora no Otoshimono doesn't ever say thanks for anyhing, because her master used to force her to act grateful while he treated her like crap, so she can't understand the honest meaning of the expression.
 * Princess Arika from Mahou Sensei Negima is normally calm and composed, including at her . When Nagi saves her life and professes his love for her, her first response is, "I do not dislike you."
 * Asti from then hentai OVA F-Force "comforts" Ash shortly before they set off on their last battle.
 * Haruhi Suzumiya doesn't know how to apologize or thank anyone. However, at one point, Kyon tells her that her the one time he saw her in a ponytail it was "so cute it was criminal," and from then on whenever she really screws up, she puts her hair in a ponytail in the next scene, since its the only way she can apologize.
 * She doesn't know how to accept gratitude either. After the concert in "Live A Live", she is thanked quite nicely by the band she helped out, and, though she handles it well in person, later feels disturbed and antsy for no reason she can think of. Kyon believes it's because she is rarely thanked for anything she does.
 * It seems like Bando from Elfen Lied can only show his gratitude by offering to kill a person of the recipient's choice, should they ever need it. As a matter of principle, he refuses to be indebted to anyone, but does not know how to handle such things because he a Career Killer to the bone.
 * Rebuild of Evangelion has a variation of this in Rei, who in the second movie reveals that she had never thanked anyone.

Film
"Bertie: No matter how this goes - I want to say, thank you. I don't know how I could thank you enough.
 * Rorschach seems to have this trouble for the longest time.
 * From The King's Speech: (paraphrased)

Lionel: {Hopefully} A knighthood?"

Literature

 * Lisbeth Salander has this problem. Understandable, as she has massive trust issues and doesn't know how to be friends.
 * Dudley Dursley in Harry Potter and The Deathly Hallows.
 * The Dothraki in A Song of Ice and Fire literally have no word for "thank you."

Live Action TV

 * Mr. Spock.
 * Sherlock is so flustered when that he can only stammer "That, uh, thing that you did--that you were prepared to do--that was...um...good." While carelessly waving a handgun around.
 * In The Big Bang Theory, Sheldon, when he

Video Games
"Clan member: We protected you, and you can't even say thank you?!
 * Jack from Mass Effect 2 has a lot of trouble coming up with a simple thanks for Shepard after her Loyalty Mission, because basically, Shepard is the first person in her life who did something good for her that she didn't have to extort by force. She does get better at it later, though.
 * Technically Shepard's the second person to do a good turn for Jack, but the first one died while doing it.
 * Likewise, the golem Shale from Dragon Age. Shale has effectively been a slave for as long as memory serves (apart from those twenty years Taken for Granite). The warden can be the first person to selflessly help the golem with anything, which makes Shale attempt to say thanks in the late game (as well as attempting to address the warden with 'you').
 * Don't forget about Sten, who, after you return his sword to him admits that he doesn't how how to thank you, then immediately says that he wants to stay with your group.
 * In Final Fantasy Tactics a 2, one mission to unlock the Dragoon job for your clan's Bangaa units involves protecting a Dragoon named Kyrra who's getting flack for it from some bullies. After your clan defeats the bullies, he offers to teach your Bangaa units how to be Dragoons as his way of saying thanks.

Kyrra: Ah... I was never good with gratitude meself."


 * Played for Laughs in Chrono Cross with Starky, an alien. When attempting to express his gratitude, he uses the phrase "You're welcome." The person he is speaking to complements his attempted courtesy, and gives him the correct phrase to use instead. A text box then pops up and says "Starky learned 'Thank You,'" as though it was an actual in-game ability.
 * Miles Edgeworth has this problem, at least in the first game. By speaking out of turn and getting herself arrested for contempt of court, Maya Fey keeps the trial going when otherwise Miles would have been found guilty of murder. During the recess, Miles hems and haws on the subject before chickening out, telling Phoenix to remind Maya to mind her manners in the courtroom. (Of course, he also paid her bail himself, so he's not all bad...)
 * Ishida Mitsunari from Sengoku Basara, due to mental instability, sullenness, extremely messed-up life and a complete lack of social graces. The Saica blue path, in which the Saica mercenaries work for him, exemplifies this: Mitsunari spends the entire campaign threatening Magoichi with horrible horrible death should she even think of betraying him. It turns out that Mitsunari values the Saica as employees, but has no real idea how to do that whole "positive reinforcement" thing and simply defaults to death treats and generally acting jealous so they stay with him. When Magoichi notes that one of his comments is practically a compliment, Mitsunari gets annoyed, but admits it was.

Western Animation

 * Squidward from SpongeBob SquarePants can't say thanks or sorry.
 * Beetlejuice has a hard time with any sort of social nicety, including but by no means limited to saying thank you.
 * In Justice League Unlimited, Batman states one of the very few things he is not good at, is saying thank you. But immediately afterwards thanks Zatanna for her help in saving Wonder Woman.