Suppressors
If you are looking at .22 only, there are many options out there, consider the overall length and diameter of the suppressor are going to be determining factors in what level of decibel reduction you can expect, and you have to factor in what type of host weapon you will be using, barrel length, semiauto, bolt action, pistol, rifle, etc. ammunition is another determining factor, typically subsonic, the heavier the better, as long as it will cycle the action if you are using a semi auto.
Walther, Sig, ISSC, and GSG all make a .22 caliber pistol with a threaded barrel, all require thier own adaptor to accept a standard 1/2X28 thread pitch suppressor, the S&W M&P series .22 A.R. type rifle is already threaded at
1/2X28 and will accept a suppressor as easily as threading the flash hider on/off.
Threading of the Ruger rifles often requires the complete removal of the front sight and can cost up to $100 for this service which should include a thread protector at that price, a must have item. The Charger having no front sight is easier to machine. I have experience shooting all the above mentioned weapons suppressed, my personal recomendation would be the GSG 1911 style .22 from American Tactical Imports. Yankee Hill and Gemtech make good suppressors, I am told Surefires new line of suppressors are very good.
If you are interested in suppressors for larger caliber pistols, I would advise you to look into Osprey, I was very impressed with the one I saw demonstrated a few weeks ago and had a chance to try myself, they also have multi-caliber units which broadens your options even further.