SSD If you don't have a big budget, How about a mug cake book (they had nice ones in the works or book people for about £3 and a nice mug (anything from a pound up) and then a few bits and bobs like choc chips, nuts and mini marshmallows if you want it to be a bit more.
I gave just the book and cup each to my cousins a couple of years ago for Christmas (aged 16-25) and they went down really well - all but the youngest were students and they still post pictures on Facebook of when they're trying a new cake or having a mug cake party. And they've bought the book for other friends to give as a present to their friends.
There are fancy mug cake kits around now but getting the book from the works and your own choice of mug (& bits of included) makes it more personal.