autodesk sketchbook symmetry doodles
first 2 are on tablet pc, last is on normal pc

Oddly, I find the tablet software handier than the pc version, but of course the pc version allows use of real wacom.

Anyway, symmetry is fascinating. It's very handy for quick character design as well, and I know some of you will tell me it's unnatural and not dynamic, however, if I were to build a 3D model I would keep it symmetrical most of the way and a symmetrical reference would be very useful.