While I remain a S&W .22 revolver believer, second place might go to this Taurus 992. It comes with .22 lr and .22 mag cylinders. Sorry about the picture. It's the only one I've got. It's the revolver on the left.
Why hasn't anyone mentioned the Diamondback? I didn't even know they made a Snake Gun in 22LR, it's a beautiful gun and by all accounts that I can find a great functioning gun. If I decide I can accept a 6 shot wheel it will be difficult not to pursue one of those little dudes.