Ruger Mark II all the way. I have a stainless steel one with a bull barrel; it's deadly accurate and a scream to shoot.
I'm not knocking the Walther at all, but the Mark II is the .22 pistol to own. There are more aftermarket items for it than you can shake a stick at.
That's one Ruger I'd put a seal of approval on over all others (well, except a 10/22 but that's a carbine and you're looking for a pistol).
First thing you need to buy with it will be clip loaders; you'll eat your thumbs up loading shells into the clips without them.
