I would say the severed head of a pig, but can only imagine there being a select audience for such a think, mainly cultists, certain types of pagans and satanists...well, Satan is only an anagram of Santa anyway, so it'll be Christmas themed in its own right!
If we're going for something a little more generic, smellies & chocolates usually are the way to go. You could probably shop somewhere like
Lush, which do nice stuff for presents (it's how I'm tackling my aunt) and there's
Hotel Chocolate as well I suppose. My aunt & uncle usually buy presents from there.
If you can find a fun present you might be sold, perhaps something you'll know make them laugh, like I got my uncle
50 Sheds of Grey last year.
For me, parents & siblings are easy, generally they write a list, plus we're all mostly into similar things, I might get my mum some CD's I think she'll like, like I did last year. But it does help that we all have similar musical tastes.