Oh god, I have a lot.
The one I've really had to hide the most (except from close friends, or my aspie boyfriend) is my obsession with searching for and collecting pictures of dead people hahaha. I have a little over 116 MB worth of crime scene/medical reference/autopsy/misc gore photos on my hard drive. I used to have more, but my computer died and I had to get a whole new one (and never made a back up...sob).
And oh boy do I love murder. Serial killers are a particular fascination of mine, as well as mental illnesses that lead to interesting homicidal/suicidal tenancies (see username for example lol).
I just like violence. In a strictly observer only sense, of course.
I still get probing questions from strangers because when I have nothing else to do and can't think of what to draw I draw bones and severed limbs/bleeding people lol. It's just an aesthetic thing, I swear.
As for what I tend to want to talk about (/monologue about): physiology, pathology, medicine, psychoactive chemistry, abnormal psychology, politics (conspiracy theories are fun lol), and misc biology facts (my friends know a lot about duck penises, for example...).
EDIT: Whoa, this is my 100th post! I have a second little rectangle now