That magical vein (I'm sure someone knows the name of it) that crosses from her chest, the front of her delts, and down her biceps... So "arms" and "chest" for me. As others have pointed out, veins in those regions don't come easily.
I know that this thread is probably dead. I love to see veins everywhere, the Freakier the better. But I love to see Bicep veins, and Leg Veins are my favorite.
I love leg veins like these:
I love it when they pop out the side of the legs like this:
Biceps