It's his birthday or Christmas or Hanukkah or your anniversary or something and you get him a gift that you think he will love.

He hates it.

-Struggles to compose his expression

-Says, "This is exactly what I've always wanted!"

-Aunt Mito raised him well

-Opens the gift and promptly bursts into raucous laughter

-"This is a gag gift, right? Good one! Okay, hand over the real thing"

-You stare at him

-"Oh."

-"Oh how nice that you thought to get me something!"

-"So beautifully wrapped, too, thank you, darling"

-(Opens it)

-(Pauses)

-"You are so sweet to have thought of me!"

-(Opens the gift and stares at it)

-"What is this, exactly, again?"

-You tell him. He nods and says, brightly, "Ohhhhh! Yes!"

-You find it shoved in the back of his closet a year later

-Opens the gift and, like Killua, laughs loudly

-"This totally sucks. What the hell were you thinking?"

-(Laughs again, this time wickedly) "Now you really owe me tonight"

-"A gift for me?"

-He opens it and looks at it

-"Thanks."

-Whatever it is, he will make a genuine effort to use it/wear it/whatever at least once just so you know he's a stellar dude

-Once he's done that, however, he immediately throws it away or has one of the Troupe take it over to the local Goodwill

-Is completely unused to presents or anyone being nice to him so he opens the gift eagerly

-He has no idea why on earth you got THIS for him

-Does not know what to say and draws a complete blank

-Decides not knowing his exact birthday is a good thing after all

-You bought him something awful on purpose because he's so nice you wanted to see if he actually would react

-He doesn't. He says "Oh goodness, now I don't even have to steal this for myself!"