Right. Morrolan just showed up and learned about Christmas, so he has no presents for anyone. For the others, if I have forgotten you (as is not unlikely), comment here.
Hidan: a good fight. See Kodachi's gift post.
Robin: A small carving of Sun Wukong, the Ever-Victorious Bodhisattva, formerly known as the Handsome Monkey King. The figure is brandishing his Any-Size Staff in a warlike pose, possibly familiar. Along with it is a scroll detailing selected stories from the Journey to the West that worthy undertook with the priest Sanzang.
Sophie: TBA
Clark: A book of thaumaturgic philosophy and theory, with annotations drawing correspondences between selected passages and the modern understanding of physics.
Hisoka: An ofuda inscribed with arcane patterns, which will enhance the power of the next spell he casts while it's active and bound around his wrist, and instructions for creating replacements. Also the translation spell, below.
Tsuzuki: An inscribed spell of translation between Japanese and English. Not a hint at all, really. Also, cookies, probably made with Sophie's assistance.
Tatsumi: same as Tsuzuki, with the annotation "I expect that you will have the opportunity to use this, after we leave this place."
Watari: same as Tsuzuki and Tatsumi, and a sheaf of papers containing notes on materials and methods pertinent to modifying an object to travel between worlds (as they discussed); a note attached reads "I look forward to attempting to put these theories into practice."
Lina: A ring inscribed with familiar patterns (the ones they were experimenting with in the fall), and notes on his experiments with it and the process he used to create it; it will enhance the power of fire spells she casts, and the waste heat energy the original pattern produced should bleed off to add to successive fire spells. He notes that he hasn't tested it exhaustively yet, so he's not sure if certain high-level spells are safe to use with it or not.
Teito: a book of legends from his world, some of which actually happened.
Jak: A set of ten potions, each of which contains a substantial dose of violet power -- comparable to Green Eco. Two more contain a smaller dose of white power.
Pell: A small glass globe on a chain which initially appears to be empty. When he touches it, however, something inside it will resonate with him; if he feeds it energy, a memory will unfold from the depths of the globe. It's undetectable to anyone else, and studying it will reveal a good deal of how it was made. The memory itself is simple gratitude, and the sense of a smile.
Kieran: A set of several glass spheres, each with a different pattern contained within. If fed energy, each can manifest the chosen pattern once, but their real purpose is in teaching; they'll project a ghost-image of their pattern at will, which a student might use to practice forming them. The patterns range from offensive strikes to more general utility spells.