Reflections done incorrectly seem to be a pet peeve of mine.
Layout. The visually pleasing way the entirety of a piece compliments itself.
The ability to draw, realistically, by hand, is...as close as I'll get to having a super power.
Shadows. Mysterious, haunting, and sometimes just down-right weird.
Perspective, MC Escher, Vanishing Points (1-4), Horizon Lines
Isometric, Planometric, and ¾ view