Michael: A variety of hair dyes. You had been planning on dyeing your hair for some time, but didn't exactly know what color you wanted, so he thought it was the perfect gift! :D
Luke: The dress you've been eyeing for a while now. You didn't have enough money to buy it yourself, and he doesn't like seeing you upset, so he bought that, and cute earrings to go with it, then took you out for a dinner date. ;)
Calum: He made you a scrap book of all his favorite memories of you two. It took a while to put it together because he kept on getting paper cuts, but once it was finished, it looked beautiful. = )
Ashton: A new IPhone. Apparently, while you were eating breakfast one morning, you accidentally dropped it in your cereal, so he thought it was a great gift, but he also got a protective case for it... Just in case! = P