Thomas: A guitar. He knows how much you've always wanted to play it, so he thought you might like one.
Minho: Mickey Mouse plushie. Minho took you to Disney Land and said you could pick out anything you wanted. You grabbed a massive Mickey Mouse stuffed animal to keep in your room and cuddle when Minho isn't there.
Newt: A silver necklace with his initials. Newt wanted to give you something as a reminder of himself when he may be in different places than you are. So he got you a necklace with an N for Newt. :)
Gally: A MacBook. Gally broke your old MacBook and really upset you. So Gally went to the Apple Store and bought you an even nicer MacBook. You forgave him.