There are quite a few .22WMR rifles floating about...although the semi-auto's suffer from a different problem...
Due to the long-straight case, most end up having stovepipe FTE's (Failure To Eject)...
few indeed are the semi-auto's that work in .22WMR, and those that do usually need to have their owner do some hand-polishing on the action.
Past .22WMR rifles (discontinued)
Marlin 922 (rock-solid, but sales sucked, so it was dropped)
Grendel R-31 (my personal fav)
H&R 700 (darn fine rifle)
Remington 597 in .22WMR (totally sucked, safety jams & other issues)
Ruger 1022M (production been started and stopped 5 times so far due to issues Ruger will not resolve due to being cheap rats)
Current .22WMR rifles...
Magnum Research's Magnum Lite
(both of the above are based off the 1022M, but far higher in quality)
Excel Accelerator (not bad, but kinda clunky)
Keltec's RMR-30 (not quite available to the public yet...)