Mine is too weird to be unusual. The most unusual special interest I once had was actually, well, would you believe tobacco, specifically cigarettes? I've never understood why people smoke, but for some reason others also found it attractive. I would read up on it a lot. Effects on your health, advertising, would you believe I even knew all the brands? I was about like eight when I had this interest. The oddest thing is I was never interested in smoking. Never for a minute. I've always disliked smoking.
As for an unusal special interest right now...hmm, I've already noticed cats aren't that unusualXDso my unusual special interest is collecting DS games.
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"Of all God's creatures, there is only one that cannot be made slave of the leash. That one is the cat. If man could be crossed with the cat it would improve the man, but it would deteriorate the cat." - Mark Twain