The full metal, fully licensed Cybergun SIG SAUER P229 Airsoft Gas Pistol made by KJW is a great practice firearm. It has all the same features as the real thing: a tactical rail, functioning decocker, SA/DA trigger and breaks down just like the real thing. If you carry a P229, this is a great way to practice on a low budget, if you are simply looking for a compact airsoft sidearm then this is wonderful option. The included magazine has a capacity of 26 rounds plus 1 in the chamber.
This is a very popular pistol with police departments for training purposes too!