While the Buckmark and Ruger suggestions are solid, something like the Ruger SR 22 is more in line with a centerfire pistol design. It really boils down to whether you like more of a target/paper punching pistol or a fun can plinker with 'combat' handgun ergonomics and controls.
Personally I found my friend's Walther P22 to be a lot more fun than the two 22/45's I had. The SR22 is simply a higher quality version of the Walther.
My CZ Kadet is a great target/plinker/trainer but they don't make them any more.