I let Buffy wrestle with my hand occationally, but never Willow. For one thing, Willow's attitude (or shall I say Torti-tude) is bad enough, and for another, Willow just doesn't care to wrestle. If you try it, it won't be called wrestling. She'll just be shredding your hand till you don't have any skin left, and then she'll run away, mad as hell.
With Buffy, I only do it when she's getting the zoomies and has "zoomed" up onto a couch and flipped over onto her back. Then I place my hand over her four feet and move them back and forth, while mock screaming and growling ("ahhhh, mrrrrrreowrrrr, graaaaarrrrr"). She goes crazy, will chew my fingers, then kick, and then use my hand to kick herself off the couch. Then she does another round of the zoomies around the house, lol. I know she enjoys it because of the way she acts; her eyes don't have that ticked-off look, they're the crazy-eyed thing she gets when she's in a funky mood and gets a little wild. Plus there's the fact that she doesn't avoid me like Willow would, lol
And both cats aren't the violent kind (unless it's Willow and she's ticked off, of course). They never bite when they play, or if they do, they know not to bite hard. It's just a kind of grab-the-skin-in-the-mouth-twist-the-skin-then-fly-away kind of thing. Just playful stuff. But they will bite when it comes to nail-clipping, and they'll bite hard, I won't lie about that, lol (well, Willow doesn't bite, she just beats my forearms with her back legs, but Buffy will bite)