Writing. I love the challenge of crossovers, trying to keep all the characters true to canon even in alternate settings.
I also like to indulge in my personal fetish for size-themed stories. Shrinking or giganticized characters interacting with differently scaled lovers.
... And here I thought I was safe from getting randomly killed. You and Shiro are my #1 enemies, I try to kill you guys but I only seem to commit suicide>.< damnit.