Oh dear, it's been an innumerable lot, can't remember all of them ^^'...but the strongest one probably is my obsession with the British isles, really, everything about the UK and Ireland (there is no worse anglophile than me, I tell you) It's been there almost my entire life, and sometimes the members of my family get really tired of me connecting everything with it But I mean, I don't mind, it gives me joy and is practically part of my lifestyle now...and others usually just think it's funny and interesting (at least at first)
Other obsessions apart from that have been less persistent, but I've had times when I haven't been able to stop thinking about for example Harry Potter, special kinds of music( I play the same songs over and over and over, sometimes up to 10 times a day, and never get enough), psychology(I love psychology, as my favourite occupation is analyzing stuff ;D), languages(still have that one, very much so, mainly because I have unbelievably easy to learn them), different TV-series( at the moment BBC's Sherlock, it's nothing short of wonderful), books, writing stories(almost every day) and so on...well, but I don't think it's all bad. Of course it's frustrating sometimes when you can't get something out of your head although you want to, or can't practice these obsessions(and of course, when everyone around you is sick hearing about it but you just want to talk and talk and talk forever p), but still, I get a lot of great things and entertainment out of it, and it's part of who I am :>