Tonks - the absence of a gift. SHE HOPES YOU APPRECIATE IT OKAY.
Remus - Draught of Peace. But it's really not that effective because this is not her forte. It's more like a Draught of ...Kinda Calm. Ish. USE IT AS YOU SEE FIT.
Byakuya - An offer to help fortify the prison to withstand ...people like her a little better. And a couple very enthusiastic recruits for guards, that she may have intimidated (but not outright threatened, this is important!) into "volunteering".
Priscilla - A small donation of ivories toward the Alliance. Feel free to embed them in her skull at a later date.
Yachiru - A cat shaped cake. (Hey, tact isn't her strong point BUT THERE IS NO ACTUAL CAT IN THE CAKE.) Some Fizzing Whizbees, and a challenge to a duel.
Freya - A cloak, and a small lantern full of magic flames. Also a howler that doesn't exactly howl - it is offering lessons in mind control. Supervised lessons, should Freya wish it. She suggests Merlin.
Ciel - How about that extension charm on his room? It's pretty sweet.
Sebastian - Self shuffling playing cards.
Arthur - A miniature Wizard's Chess set. The Knights look like they might be related to that knight he already has. In fact, should they be in the same room - they might occasionally argue and attempt to outdo each other with feats of strength. And some pepper imps.
Merlin - A pair of enchanted coins, similar to the ones that Draco used to communicate with Rosmerta. They can be used by Merlin/whoever he wishes. They will not communicate anything back to her - feel free to have Remus test them!
Heine - A magical chain for his ...guns. It's nearly unbreakable by normal means.
Miata - An interactive ball of light.
Shirley - A seemingly small telescope that unfolds into a decent sized one. It's also a Foe Glass (http://harrypotter.wikia.com/wiki/Foe-
Sam - Some Felix Felicis (http://harrypotter.wikia.com/wiki/
Ukitake - A teacup that actually multiplies itself for however many tea drinkers you have at your table. Or wherever. And a selection of green teas.
Hitsugaya - A handwritten note of apology.
Kujo - A ridiculous set of boxers with constellation patterns on them. Also, they change color whenever they feel like it.
Trevor - A handwritten note of apology.
Alphonse - A book of Alchemy from the Wizarding World.
Spencer Reid - Omnioculars (http://harrypotter.wikia.com/wiki/