I LOVE Cyberskin for its real feel.
But out of the rest listed, I'm going for wood. I love the beautiful timber pattern in a lot of the wooden toys, but they must have a curve.
I really like silicone too, but it's getting on my nerves lately with the amount of friggin lint it catches.
When ya have pets inside, there is ALWAYS stray hairs around.
I have found a new fondness for metal now too. I'm liking toys that don't pick up everything.
I like silicone best, with plastic and glass tied for second (I can just hear someone out there wondering how I can possibly equate the two, hahaha!). But I've only played with a few material types, so I suppose my answer may change if I ever get around to trying more out.