Unless you want cheap practice for an M&P carry, I'd suggest Ruger Mk2/3 or Buckmark. You just can't get any better for a plinker unless you need a target gun which is going to cost you a lot more. My Mk 2 is 1/2" at 25 yards accurate. I have a scope on it.
At the last gun show, I was looking for the SR22 I bought, but this table where I bought it had a stainless Mk3 for the same price and I nearly bit on that. I really wanted the SR22 for use as a pocketable kit gun, though, and it's is a dandy for that. I have a stainless kit gun revolver, but it's a little big and heavy for pocket carry. It is quite accurate, though, as accurate and a little easier to shoot than the SR22. I thought about that Mk3 just to have one with iron sights as I really don't wanna take the 2x scope off my Mk2, too accurate and fun and a good squirrel gun. What I'll likely get next is a Buckmark just because I don't have one. I can get one for under 300 bucks at Academy any time I'm ready to buy. I have a half dozen other .22 handguns, but the little revolver, the SR22, and my Mk 2 seem to get all my attention as they're the most accurate, well made, and reliable. I do need to add a Buckmark to my collection, though. Those are just as nice a shooter as the Ruger Mk2/3. I really have no desire for a M&P, though some of the other Smiths are nice. I handload, so don't need a .22 version of a carry. I don't carry an M&P anyway, though.